First Step: Preheat and prepare baking pan Set your oven to 350°F (175°C). Grease and flour a 9-inch round cake pan using gluten-free flour, or line it with parchment paper to prevent sticking. Make sure all ingredients are ready and at room temperature for best results.

Second Step: Mix dry ingredients In a large bowl, whisk together your gluten free flour, baking powder, unsweetened cocoa powder, and salt thoroughly. This ensures even distribution of leavening and flavor components for consistent batter.

Third Step: Combine wet ingredients In a separate bowl, beat eggs (or flax eggs for vegan), granulated sugar, vegetable oil, milk (or plant milk), and vanilla extract until smooth and fully combined. This creates a cohesive wet base to blend with dry ingredients.

Fourth Step: Incorporate dry into wet Gradually add the dry mix to the wet ingredients, folding gently just until combined. Avoid over-mixing to maintain a tender crumb and good cake rise.

Fifth Step: Divide and flavor batters Separate the batter evenly into three bowls. Leave one plain for vanilla, add strawberry puree to the second for fruity flavor, and stir in additional cocoa powder to the third bowl to intensify the chocolate layer.

Sixth Step: Layer and swirl the batter Alternately spoon the vanilla, strawberry, and chocolate batters into the cake pan in small dollops. Use a skewer or butter knife to gently swirl through the layers, achieving the signature marbled effect without blending the colors too much.

Seventh Step: Bake the cake Bake in your preheated oven for 35-40 minutes or until a toothpick inserted in the center comes out clean. Adjust baking time as needed for your oven and altitude.

Final Step: Cool and serve Let the cake cool in the pan for 10 minutes before transferring it to a wire rack to cool completely. Serve as is or with your favorite gluten free frosting. Adjust ingredients as needed for vegan or low-calorie preferences at any step.