Preheat oven to 350°F
Place 2 tablespoons butter in a 9-inch round cake pan or divide butter among 8 muffin cups, placing about 3/4 teaspoon butter in each cup. Place pan or muffin tin in oven until butter is melted, from 1 to 2 minutes. Place on a heatproof countertop.
Brush bottom and sides of pan or muffin cups with melted butter. Sprinkle 2 tablespoons brown sugar into butter on bottom of pan or about 3/4 teaspoon brown sugar into each muffin cup. Stir brown sugar into butter to evenly distribute. Evenly scatter blueberries over brown sugar mixture. They will form a thick layer.
In a medium-size bowl, using a fork, stir flour with baking powder, cinnamon and salt.
In a large bowl, using an electric mixer set on medium-high, beat 1/2 cup butter until creamy, about 1 minute. Gradually beat in granulated sugar until mixture is pale and texture resembles creamy whipped butter, at least 2 minutes. Beat in eggs, one at a time, beating well between additions and scraping down sides of bowl. Beat in almond extract and vanilla.
Reduce speed to low and gradually beat in one-third of flour mixture, then half of milk. Repeat additions, ending with flour mixture, beating just until blended. Batter will be quite thick.
Spoon evenly over berries. If using muffin cups, divide batter evenly among them. Gently smooth batter to completely cover berries.
Bake in centre of 350F oven until cake edge begins to pull away from side of pan and cake springs back when lightly touched in centre, from 40 to 45 minutes for cake and 20 to 25 minutes for muffins.
Remove from oven and let stand in pan or muffin cups for just 5 minutes, then run a knife around outside edge of cake. Invert onto a large cake plate or flat surface for muffin cups. Serve warm or at room temperature. If making more than 1 day ahead, cover with a tent of foil and refrigerate. Briefly warm in microwave or bring to room temperature before serving.