Blueberry-Almond Coffeecake

Preheat oven to 350 °F and butter a 2- to 2 1/2-quart (2 1/4 inches deep) ceramic or glass baking dish. Sift together flour, baking powder, and salt. Beat together butter and 1 1/4 cups sugar with an electric mixer until light and fluffy. Beat in whole eggs, 1 at a time, then vanilla. Alternately add flour mixture and milk in batches, beginning and ending with flour mixture and beating on low speed after each addition until just incorporated. Fold in berries. Spoon batter into baking dish, spreading evenly. Lightly beat egg white with a fork and add remaining 3 tablespoons sugar and almonds, stirring to coat. Spoon topping over batter and bake in middle of oven until golden brown and a tester inserted in center comes out clean, 50 minutes to 1 hour. Cool in pan on a rack 10 minutes.