1/2 cup (1 stick) unsalted butter, room temperature
3/4 cup sugar
1 teaspoon finely grated orange or tangerine zest
2 large eggs, separated
1 teaspoon Vanilla Bean Paste or 2 teaspoons Rain’s Choice pure Vanilla Extract
1–1/2 cups all-purpose unbleached flour
1/2 teaspoon baking powder
1/4 teaspoon salt
1/4 cup milk
12 teaspoons jam or lemon curd
1–1/2 cups powdered sugar
1/4 cup freshly squeezed orange or tangerine juice
Squeeze of fresh lemon juice (amount to taste)
Preheat oven to 350 degrees F. Butter a standard 6-cup muffin tin; set aside.
In a medium bowl, beat butter, sugar and zest until light and fluffy. Beat in egg yolks one at a time until creamy; set aside. Into a small bowl, sift together flour baking powder and salt. Add flour mixture and milk to butter mixture; set aside.
In a clean bowl, whisk egg whites to soft peaks; fold into batter. Divide half of the batter among muffin cups. Make an indentation in the middle of each; fill with 2 teaspoons jam. Top with remaining batter.
Bake until a cake tester inserted in top cake layer comes out clean, about 30 minutes. Unmold cakes and transfer to a wire rack to cool. In a small bowl, whisk together powdered sugar and juices. Place rack over parchment or wax paper; drizzle cakes with glaze. Let glaze set up then drizzle again until glaze is used.
Find it online: https://vanillaqueen.com/jam-cakes/