How to Make It
Using a serrated knife, cut off rounded tops of each pound cake to make flat surfaces about 1 1/2 in. thick. Using a 2 1/4- by 2 3/4-in. egg-shaped cookie cutter, cut out 3 egg-shaped cakes from each pound cake, pressing down on edges of cutter to cut all the way through to bottom. Save cake scraps for other uses.
Cut each egg cake in half horizontally. Using a circular measuring half-teaspoon, carve out a hole about the same size as the teaspoon in center of each egg cake top and bottom to make a half-sphere; check to be sure holes will line up once put back together and be careful not to poke a hole through cakes.
Put a rounded 1/2 tsp. lemon curd in each cavity. Carefully place egg cake tops back on cake bottoms.
Mix powdered sugar, corn syrup, 1/3 cup plus 2 tbsp. hot water, and the lemon extract in a medium heatproof bowl. Set over a saucepan with 1 in. simmering water over low heat. Whisk constantly until icing reaches about 100° on an instant-read thermometer. Add food coloring if you like to create a pastel color. Icing should be thin and pourable (test a small spoonful over a scrap piece of cake); if too thick, add hot water 1 tbsp. at a time. Keep icing over low heat. (When icing sits without movement, it begins to form a skin on top; simply stir to make smooth again.)
Set cakes on a cooling rack set over a rimmed baking sheet, brushing off crumbs. Pour about 1/3 cup icing over each egg cake, starting from edges and moving to center, making sure to cover sides. Let stand until icing is set and dry to touch, about 10 minutes.
Put some white icing coloring in each of two small bowls and add a little pink to one and a little yellow to the other to create pastels. Paint cakes with coloring, using a small paintbrush to create designs such as chevrons and stripes. To apply dots, use a cotton swab. Sprinkle with gold pearl dust if you like.
Make ahead: Up to 4 days, wrapped airtight.
*Find a set of plain oval cutters, such as Ateco; decorating brush set, such as Wilton; gel paste food coloring, such as AmeriColor; and gold pearl dust, such as Wilton at amazon.com, craft stores, and specialty baking stores.