- 1/2 cup plus 2 tablespoons (1 1/4 sticks) unsalted butter, room temperature, plus more for pan
- 2 cups all-purpose flour, plus more for pan
- 4 summer squash (combination of zucchini and yellow squash)
- 1 cup shelled unsalted pistachios, coarsely chopped
- 1 teaspoon salt
- 1 1/2 teaspoons baking powder
- 1 1/4 cups sugar
- 4 large eggs
- 1 teaspoon vanilla extract
- 2 teaspoons fennel seeds
- Preheat oven to 425 degrees. Generously butter a 9-by-5-inch loaf pan; dust with flour, tapping out excess. Using a box grater, coarsely grate both types of squash. Place grated squash in a piece of cheesecloth (or clean thin dish towel); squeeze out as much liquid as possible.
- Spread pistachios on a rimmed baking sheet; toast in oven 5 minutes. Transfer sheet to a wire rack to cool. Sift together flour, salt, and baking powder into a medium bowl.
- With an electric mixer on medium-high speed, beat butter and sugar until pale and fluffy, 3 to 5 minutes. Add eggs, 1 at a time, beating well after each addition. Beat in vanilla. Add flour mixture; beat until just combined. Fold in squash, pistachios, and fennel seeds.
- Transfer batter to prepared pan. Bake 10 minutes. Reduce heat to 350 degrees. Continue to bake until cake is golden brown and a cake tester comes out clean, about 1 hour. Transfer pan to a wire rack to cool 10 minutes. Turn out cake onto rack to cool completely.
Cake can be stored at room temperature, wrapped in plastic, up to 2 days.