Preheat oven to 325°F (170°C).

In the bowl of a stand mixer fitted with the paddle attachment, beat butter and marzipan at medium-low speed until smooth and creamy, about 1 minute. Add granulated sugar, and beat at medium speed until light and fluffy, 2 to 3 minutes, stopping to scrape sides of bowl. Add eggs, one at a time, beating until combined after each addition and stopping to scrape sides and bottom of bowl. Beat in extracts.

In a medium bowl, whisk together flour, poppy seeds, baking powder, and salt. With mixer on low speed, add flour mixture to butter mixture in three additions alternately with milk, beginning and ending with flour mixture, beating until combined after each addition and stopping to scrape sides and bottom of bowl.

Spray a 12-cup Bundt pan with baking spray with flour. Spoon batter into prepared pan, leveling as needed. Firmly tap pan on a kitchen towel-lined counter 5 to 7 times to settle batter and release any air bubbles.

Bake until golden and an instant-read thermometer inserted near center registers 205°F (96°C), about 1 hour. Let cool in pan for 10 minutes. Invert cake onto a wire rack, and let cool completely.

When ready to serve, garnish with confectioners’ sugar, if desired. Store in an airtight container for up to 3 days.