Preheat your oven to 350 F. Grease your 8x8 pan with butter, then line the bottom with parchment. Create a foil divider to create two separate but equal compartments in the pan. (The cake batter will be thick and not runny). Re-grease over the parchment and foil
To make the sponge, cream the butter in a stand mixer fitted with the flat beater. Scrape down the inside of the bowl.
Add the sugar a couple of tablespoons at a time, mixing well between each addition. Scrape the bowl again, then mix on medium for a couple of minutes until light and fluffy.
In a small bowl combine your flour, baking powder and salt to essential create a self-rising flour blend
Now, break your eggs into a separate bowl, add your extract and whisk together. Beat slowly into butter mixture, a tablespoon at a time, adding in some flour after the first couple of additions to keep the mixture from curdling (be watchful and go slow - use flour to temper the butter-egg reaction)
Whisk in the remainder of the flour, a good pinch of salt, and the almond flour into the bowl. Add 2 tsp of coconut or other milk and stir until just combined.
Transfer the entire mixture into a bowl atop a kitchen scale and weigh the cake mixture only. Remove half the mixture in weight back to the mixing bowl. Color your separate cake mixtures however you like. For this recipe we used pink and yellow food coloring to get the traditional battenburg look. If you are using the freeze-dried strawberries, mix these into the pink side (or one side)
Spread your mixtures into either side of the cake pan being careful to level the top and get batter to the edges. I found a flexible rubber spatula plus small cake spatula to be most helpful with this
Bake your cake for 20-25 minutes or until edges just start to turn golden and a toothpick inserted comes out clean. The cake should spring back lightly when pressed. My cake takes about 20-21 minutes and the temp inside is about 190 F at completion
Set the tin on a wire rack and run a round bladed knife around the edges to loosen. Let sit until barely warm, then remove cake sides to the cooling rack until room temperature. Your cake must be completely cool before proceeding