1. For the streusel: In standing mixer fitted with flat beater, combine flour, sugars, cinnamon, and salt on low speed until well combined and no large brown sugar lumps remain, about 45 seconds. Add butter and mix on low until mixture resembles wet sand and no large butter pieces remain, about 2 1/2 minutes. Transfer streusel to small bowl and set aside.

2. For the cakes: Adjust oven rack to lower-middle position; heat oven to 350°F. Line muffin pan with paper liners.

3. Whisk flour and baking powder in small bowl to combine; set aside. In standing mixer fitted with flat beater, cream butter, sugar, salt, and lemon zest at medium-high speed until light and fluffy, about 3 minutes; using rubber spatula, scrape down bowl. Beat in vanilla until combined, about 30 seconds. With mixer running at medium speed, add eggs one at a time; beat until partially incorporated, then scrape down bowl and continue to beat until fully incorporated (mixture will appear broken). With mixer running on low speed, gradually add flour mixture; beat until flour is almost fully incorporated, about 20 seconds. Disengage bowl from mixer; stir batter with rubber spatula, scraping bottom and sides of bowl, until no flour pockets remain and batter is homogenous; batter will be very heavy and thick. Using rubber spatula, gently fold in blueberries until evenly distributed.

4. Transfer batter to prepared muffin cups; with spoon, spread batter evenly to cup edges, gently pushing in to fill all gaps, and smooth surface. (Note: Batter will come up to top of papers.) Squeeze handful of streusel in hand to form large cohesive clump; break up clump with fingers and sprinkle streusel evenly over batter. Repeat with remaining streusel. Bake until deep golden brown and toothpick or wooden skewer inserted into center of cake comes out clean, about 35 minutes. Cool until just warm or to room temperature, about 1 hour.

Makes 12 individual servings