Gluten-Free Korean Castella Sponge Cake: Perfectly Fluffy and Light

The star of the recipe is the meringue. Properly whipped egg whites give the cake its height and cloud-like texture. Lemon juice strengthens the foam, making it more stable during folding and baking.

Step-by-Step Instructions

Step 1: Prepare Your Pan and Oven

Line an 8x8-inch square pan with parchment paper on all sides, leaving enough excess to lift the cake out later. Preheat your oven to 150°C (300°F). Castella bakes low and slow for a more even rise and a smooth exterior.

Step 2: Combine the Dry Ingredients

Sift the gluten-free cake flour, starch, and salt together twice. This ensures the mixture is fine and distributes evenly into the batter without forming lumps.

Step 3: Make the Egg Yolk Base

In a mixing bowl, whisk the egg yolks and sugar until pale and thick. Once the mixture turns a light yellow shade, slowly drizzle in the oil while whisking. Add the warm milk and vanilla extract, blending until the mixture looks smooth and glossy.

Step 4: Incorporate the Dry Ingredients

Add the sifted dry mixture into the yolk batter in two additions. Use a spatula to fold gently, stopping as soon as you see no visible dry spots. Be careful not to overmix here, as it can cause the batter to lose its airiness.

Step 5: Create a Stable Meringue

Place the egg whites and lemon juice in a clean bowl. Beat at medium speed until the mixture becomes frothy, then slowly incorporate the sugar. Continue mixing until the meringue reaches firm, glossy peaks. The foam should hold its shape but not look dry.

Step 6: Fold the Meringue into the Batter

Start by adding one-third of the meringue into the yolk mixture and fold gently to lighten the batter. Add the remaining meringue in two more additions, folding with slow, sweeping motions. Avoid stirring or pressing down, or you may lose essential air.

Step 7: Pour and Tap

Pour the batter into the prepared pan. Tap the pan lightly on the counter to release trapped air bubbles that could create holes or tunnels inside the cake.

Step 8: Bake Slowly and Evenly

Place the pan in the oven and bake for 65 to 75 minutes. The top should turn a warm golden color and spring back when touched. If the surface darkens too quickly, you may loosely place a piece of foil on top during the last 20 minutes, but only if necessary.

Step 9: Cool the Cake Correctly

After baking, let the cake rest in the pan for around 10 minutes. Then lift it out with the parchment paper and place it on a wire rack to cool completely. Allow it to cool completely before slicing to maintain a clean crumb.

Tips for the Perfect Gluten-Free Castella Texture

Use Fine Starches for Softness

Cornstarch, tapioca, and potato starch all help produce a lighter crumb. Avoid blends that rely heavily on grainy flours like sorghum or millet for this recipe, as they can weigh down the structure.

Keep the Temperature Low

Castella rises slowly, so a hotter oven can cause a dramatic rise followed by collapse. Low heat preserves moisture and promotes slow, even expansion.

Avoid Overmixing the Batter

Gluten-free flours don’t have gluten to toughen up, but overmixing still destroys air bubbles. The more patient your folding, the fluffier the final cake.

Don’t Skip the Sifting

Sift the dry ingredients twice. This step prevents dense pockets and ensures the batter stays light.

Use Room-Temperature Eggs

Cold egg whites don’t whip as effectively, and yolks don’t blend as smoothly. Bringing eggs to room temperature improves both structure and color.

Flavor Variations You Can Try

Matcha Castella

Add 1 to 1½ tablespoons of matcha powder to the dry ingredients. Sift well to prevent clumping. Matcha pairs beautifully with the subtle sweetness of the sponge.

Honey Castella

Replace 2 tablespoons of sugar in the yolk mixture with honey. Warm the honey slightly before adding so it blends evenly.

Black Sesame Castella

Add 2 tablespoons of finely ground black sesame powder. This gives a nutty, aromatic twist.

Vanilla Milk Castella

Double the vanilla extract and use warm vanilla-infused milk for a richer fragrance.

Troubleshooting Guide

Cake Deflates After Baking

Possible cause: Overfolding, too hot oven, or under-whipped meringue.

Solution: Whip egg whites to glossy firm peaks, keep oven at low temperature, and fold more gently.

Dense or Wet Bottom Layer

Possible cause: Heavy flour blend or insufficient folding.

Solution: Use a finer gluten-free cake blend and ensure the meringue is incorporated evenly without big pockets.

Cracks on Top

Possible cause: Oven too hot or batter mixed inconsistently.

Solution: Reduce heat slightly or stir the yolk mixture more thoroughly before adding meringue.

Sticky or Gummy Texture

Possible cause: Too much moisture or underbaking.

Solution: Extend baking time by 5–10 minutes or reduce milk slightly if using a very high-moisture plant milk.

Serving Suggestions

Korean Castella is enjoyed plain or with light additions. You can cut it into warm cubes, serve it with fresh fruit, or pair it with tea. Its soft texture also makes it suitable for layered desserts, trifles, or fruit-filled sponge cups.

Final Thoughts

Baking a gluten-free Korean Castella sponge cake that stays moist, fluffy, and beautifully tall is absolutely achievable with the right methods. When you select a fine flour blend, whip your meringue properly, fold gently, and bake slowly, the result will rival any bakery version. This cake is a wonderful addition to your gluten-free recipe collection and a perfect example of how Asian baking techniques adapt beautifully to gluten-free methods.