Preheat the oven to 350 degrees. Spray two 8" round cake pans and
place a parchment circle at the bottom of the pan. Set aside.

In a medium bowl combine the flour, baking soda, baking powder, and salt. Mix well and set aside.

In a large bowl cream together the butter and sugar until it is smooth.
Add in the eggs, vanilla extract, and lemon extract and mix well.

Add half the flour mixture to the butter mixture and mix until combined.

Add in the milk and mix well. Add the remaining flour and mix until just combined.

Divide the batter between 6 bowls. Dye one red, one orange, one yellow, one green, one blue, and one purple. Mix well.

Pour half the red batter in the center of one of the prepared pans. Carefully pour half the orange batter directly into the center of the orange batter. Then carefully pour half the yellow batter in the center of the orange batter. Repeat with the green, then blue, then purple.

In the other pan pour the remaining purple batter in the center of one of the prepared pans. Carefully pour the remaining blue batter directly into the center of the purple batter. Then carefully pour the remaining green batter in the center of the blue batter. Repeat with the yellow, then orange, then red.

Bake for 35 minutes.

Remove from oven and allow to cool 10 or 15 minutes. Run a butter knife around the edge of the cake and remove from pan. Cool completely on a wire rack.

To make the frosting place the butter in a large bowl. Beat with a mixer on medium high speed until smooth.

Add in the powdered sugar a half cup at a time.

Add in the vanilla extract and the milk and mix well. Add additional powdered sugar if needed.

To assemble the cake place on layer on a cake round. Top with 1/2 cup of frosting. Pipe a border of frosting around the edge and then add the lemon curd in the middle and spread to the edges.

Top with the second layer of cake.

Cover the cake on the top and sides with the buttercream frosting. Pipe a pretty border on the top edge.

Pour rainbow sprinkles all over the top of the cake.

Slice the cake and enjoy!