Whisk together melted butter, sugar, Amaretto, and almond extract in a large mixing bowl.
Whisk in eggs one at a time until smooth.
Stir in flour, baking powder, and salt until almost fully incorporated; fold in almond paste and sliced almonds.
Cover dough and chill for 30 minutes.
Preheat oven to 350°F and line two baking sheets with parchment paper. Divide dough in half and shape dough into 2 (10-by-4-inch) loaves on prepared baking sheets.
Top with sliced almonds, pressing gently into dough, and sprinkle with sugar. Bake for 24 to 25 minutes, until pale golden.
Carefully transfer loaves to a wire rack and cool for 15 minutes.
Using a serrated knife, cut loaves into ½-inch slices. Place slices cut side down on baking sheets; bake 10 minutes. Turn slices over and bake for 10 minutes more or until golden.
Cool completely on wire racks. Store at room temperature in an airtight container.
