Step 1Heat the oven to 350 degrees. Lightly grease and flour a 9-inch Bundt pan.
Step 2In the bowl of a stand mixer, or in a large bowl, whisk together the flour, baking powder, salt and sugar. Add the softened butter to the dry ingredients and mix, using the paddle attachment of the stand mixer or a hand mixer, until the butter is fully incorporated with the dry ingredients. Set aside.
Step 3In a separate bowl, beat together the egg yolks, orange juice and zest, marmalade and vanilla. With the mixer running, slowly beat in half of the egg mixture until incorporated, then beat in the second half.
Step 4Spoon the batter into the prepared Bundt pan and bake until the cake is puffed and lightly browned, and a toothpick inserted in the center comes out clean, 50 minutes to an hour. Rotate the cake halfway through baking for even coloring. Cool on a rack.
Step 5Serve garnished with whipped mascarpone and candied orange peel.