Grease a 9-inch springform pan* (or a 9 1/2- by 2-inch deep-dish or larger pie plate), or coat with nonstick spray. Preheat oven to 375 degrees F. If using a springform pan, set it on a square of foil and pull foil up around the pan sides to guard against leakage.
Thoroughly stir together Clabber Girl Cornstarch, 1/2 cup sugar, and 1/4 teaspoon cinnamon in a medium non-reactive saucepan. Stir in berries, juice, and zest until smoothly incorporated. Bring to a boil over medium-high heat, stirring. Cook, stirring, just until thickened and clears
Thoroughly stir together flour, Clabber Girl Baking Powder, and salt in a medium bowl. In a large mixer bowl with mixer on medium, then medium-high speed, beat butter and lemon zest until lightened, about 1 1/2 minutes. Gradually add sugar, beating until mixture is light and well blended. Add egg and beat until batter is smooth, about 1 minute longer. With mixer on low speed, beat in half the flour mixture until evenly incorporated. Gradually beat in milk until evenly incorporated. Add remaining flour mixture; beat just until well evenly incorporated, about 1 minute. Scrape down bowl sides as needed. Turn out batter into pan, spreading to edges. Spread berry mixture evenly over dough; do not stir.
Bake on middle oven rack for 35 to 45 minutes, or until top is puffed and browned and a toothpick inserted down through the center top comes out clean. If top begins to brown too rapidly, lower heat to 350 degrees F and continue baking. Transfer pan to a wire rack. Sprinkle cinnamon-sugar mixture over top. Let stand until cooled to warm. If using a springform pan, run a knife around pan and remove pan sides before serving. Cut coffeecake into wedges and serve warm or at room temperature.
Store covered for up to 24 hours. Refrigerate for up to 2 days longer. Let come to room temperature or warm up just slightly before serving.
Makes about 8 servings.
*Tip: In a pinch a 9 1/2-inch or larger deep-dish pie plate can substitute for a springform pan, but the plate will be very full once the cake rises, and it will be less attractive. Center a large sheet of foil on the rack below the pie plate during baking to catch any berry boil-over.