Step 1Position a rack in the lower third of the oven and heat the oven to 350 degrees. Lightly butter and flour a 9-by-5-inch loaf pan, knocking out the excess flour.
Step 2Sift together the flour, baking powder and salt twice. In a small bowl, combine the eggs and vanilla and whisk together just to combine.
Step 3In the bowl of a stand mixer fitted with the paddle attachment, beat the almond paste on low speed until it breaks up. This can take up to a minute, depending on how soft and warm it is. Slowly add the sugar in a steady stream, beating until incorporated. If you add the sugar too quickly, the paste won't break up as well.
Step 4Cut the butter into 1-tablespoon pieces. Continue on low speed while adding the butter, a tablespoon at a time, for about 1 minute. Stop the mixer and scrape down the sides of the bowl with a rubber spatula. Then turn on the mixer to medium speed and beat until the mixture is light in color and fluffy, 3 to 4 minutes. With the mixer still on medium speed, add the eggs in a very slow, steady stream and mix until incorporated. Stop the mixer and again scrape down the sides of the bowl. Turn on the mixer again to medium speed and mix for 30 seconds more.
Step 5Add the citrus zests and mix in with a wooden spoon. Add the flour mixture in two batches, stirring after each addition until incorporated. Scrape down the sides of the bowl one last time, then spoon the batter into the prepared pan and smooth the surface with an offset spatula.
Step 6Bake until the top springs back when lightly touched and a cake tester inserted in the center comes out clean, 60 to 65 minutes. Let cool in the pan on a wire rack for 5 to 7 minutes while you make the glaze.
Step 7To make the glaze, stir together the lemon and orange juices and the sugar in a small bowl. Place the wire rack holding the cake over a sheet of waxed paper or aluminum foil to catch any drips of glaze, and gently invert the cake onto the rack. If the cake does not want to release, run the tip of a small knife around the edge to loosen it. Brush the entire warm cake with the glaze, then let the cake cool completely on the rack. The cake breaks apart easily when warm, so don't attempt to move it.
Step 8When the cake is cool, transfer it to a serving plate, using two crisscrossed icing spatulas or the base of a two-part tart pan to lift it. Serve at room temperature. The cake will keep, well-wrapped, for 1 week in the refrigerator.