Candied orange slices are a sweet complement to this richly textured cake made with chopped almonds and nutty semolina flour. Look for semolina flour at Italian and gourmet markets or health-food stores.
Preheat oven to 350 degrees. Grease sides of a 10-inch tube pan with removable bottom.
Beat egg whites until stiff, approximately 7 minutes. Add sugar, then yolks, and beat until stiff, adding baking powder along the way. In a stand mixer fitted with the paddle attachment, beat butter, condensed milk, vanilla powder, and the orange zest until smooth.
Fold the whipped butter mixture into the egg white mixture. Fold in cake flour, semolina flour, and chopped almonds.
Bake 30 to 35 minutes. Cover with aluminum foil and bake an additional 10 to 20 minutes.
While the cake is in the oven, make the candied orange slices: Line a baking sheet with parchment paper. Arrange orange slices in a single layer and generously dust with confectioners' sugar. Transfer to 350-degree oven and bake until bubbling and lightly golden around edges, about 20 to 30 minutes.
Turn off oven and leave cake in oven for 30 minutes. Remove cake, place on a cooling rack, cover with foil and a plate to cool for 1 hour.
Remove cake from pan and serve with candied orange slices and whipped cream.