Preheat your oven to 350°F (177°C). Grease a 9x13-inch cake pan and line the bottom with parchment paper for easy removal.

In a medium bowl, whisk together the cake flour, baking powder, and salt. Set aside.

If using the cake flour substitute: measure 2 cups all-purpose flour, remove 4 tablespoons of flour, then replace it with 4 tablespoons cornstarch. Sift well before using.

In a large mixing bowl, whisk together the melted butter and granulated sugar until smooth and combined.

Add the egg whites and vanilla extract. Whisk until the mixture becomes lighter and slightly frothy.

Add half of the dry ingredients to the bowl and stir gently to combine. Pour in half of the milk and mix again. Repeat with the remaining dry ingredients and milk, stirring until just combined.

Fold in the sourdough discard until fully incorporated. Do not overmix.

Pour the batter into the prepared 9x13-inch cake pan and smooth the top evenly.

Bake for 30–38 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs.

Allow the cake to cool before assembling the cakes.

In a large mixing bowl, beat the softened cream cheese and butter together until completely smooth and creamy, about 2 minutes.

Add the vanilla extract and salt.

Gradually mix in the sifted powdered sugar, one cup at a time, until fully combined.

Beat on medium-high speed for 2–3 minutes until light and fluffy.

There are a couple different ways to make these trendy dot cakes depending on the jars you’re using.

For small 4-ounce jelly jars, use the jar opening as a guide or use a biscuit cutter that fits the size of the jar.

Cut rounds from the cooled cake and place one cake round into each jar.

Add a layer of frosting on top and smooth it flat.

Frost the top so it is level with the rim of the jar.

Flip the frosted side directly into a bowl of nonpareil sprinkles to coat the top completely.

For larger 13-ounce jelly jars, use a biscuit cutter that fits inside the jar opening.

Cut circles from the cake. If needed, carefully slice the cake rounds horizontally to create thinner layers.

Place one cake layer into the bottom of the jar.

Pipe or spread a layer of frosting over the cake.

Repeat with additional cake layers and frosting until the jar is filled nearly to the top.

Spread frosting evenly across the very top so it is flush with the rim of the jar.

Turn the jar upside down and dip the frosted top into a bowl filled with nonpareil sprinkles until fully coated.

Flip upright and refrigerate until ready to serve.

Store assembled dot cakes covered in the refrigerator for up to 5 days.

For the best texture and flavor, allow the jars to sit at room temperature for about 20–30 minutes before serving.