Preheat the oven to 350ºF. Grease and flour an 8-cup muffin tin.
Combine the flour, cornmeal, baking powder, cinnamon, and salt in a small bowl. Whisk to blend.
Beat the butter, sugar, and lemon zest in a small bowl until creamy. Beat in the egg and vanilla.
Add the flour mixture and milk to the bowl. Beat 30 seconds until blended. Gently stir in half of the mulberries.
Divide the batter into the prepared muffin tin cups.
Scatter an even amount of the remaining mulberries over each cup, and press them gently to stick into the batter.
Bake 28 minutes, until golden around the edges, and a skewer inserted in the center comes out clean. Let cool at least 20 minutes. Dust with confectioners’ sugar, if desired, before serving.