Preheat the oven to 375°F. Lightly butter a 12 cup standard muffin tin or line it with muffin liners.
1 stick (8 tablespoons or 113 grams or 4 ounces) unsalted butter, melted and cooled
In a medium to large sized bowl, whisk together the flour, sugar, poppy seeds, baking powder, salt, baking soda, and orange zest, breaking up any clumps of orange zest.
2 cups (250 grams or 8.8 ounces) bleached, all-purpose flour, ½ cup (100 grams or 3.5 ounces) granulated sugar, ¼ cup poppy seeds, 2 teaspoons baking powder, ½ teaspoon salt, ¼ teaspoon baking soda, two small or one medium orange, finely zested and juiced
Add the orange juice to a 2 cup measuring cup. You should have about ¼ cup.
two small or one medium orange, finely zested and juiced
Add the milk to this same measuring cup to total 1 cup (8 ounces).
¾ cup whole milk, plus a little more or less to total 1 cup of liquid
Add the eggs and orange liqueur to the measuring cup and whisk until uniform in color.
2 large eggs, 1 teaspoon Grand Marnier or other orange liqueur
Add the cooled butter and wet ingredients to the bowl with the dry ingredients and mix them together gently just until there are no more pockets of dry ingredients. Do not overmix the batter.
1 stick (8 tablespoons or 113 grams or 4 ounces) unsalted butter, melted and cooled
Use a large cookie scoop or ¼ cup measure to fill the muffin tin about three-quarters full.
Bake for 18 to 20 minutes, until the tops of the muffins have begun to turn golden and a toothpick inserted into the center of one comes out clean.
Cool the muffins in the muffin tin for 5 minutes, then let them finish cooling on a cooling rack.
These orange and poppy seed muffins can be stored in an air tight container at room temperature for 3 to 5 days. Once cool, muffins can be frozen (without the glaze) in a freezer bag for 3 to 6 months.