lighter, airy pound cake

INGREDIENTS

• 1/2 pound (2 sticks or 8 ounces or 226 grams) butter, at room temperature, plus more for greasing the pan
• 1 1/2 cups (200 grams) all-purpose flour, plus more for dusting the pan
• 1/2 teaspoon (3 grams) baking powder
• Salt
• 4 large eggs, separated
• 3/4 cup plus 2 tablespoons (186 grams) sugar
• 1 tablespoon Cognac [brandy works as well, as does rum, as would one teaspoon of an extract of your choice]
• 1 1/2 teaspoons grated lemon zest.