Lemon Blueberry Coffee Loaf Cake

Preheat oven to 350°F. Grease and line a 9×5-inch loaf pan with parchment paper. In a medium bowl, whisk together flour, baking powder, and salt. In a separate bowl, beat together sugar, mayonnaise, eggs, melted butter, lemon juice, zest, and vanilla until smooth. Add dry ingredients to wet ingredients and mix until just combined. Gently fold in blueberries. Pour batter into prepared loaf pan and smooth the top. Mix ingredients for crumb topping and sprinkle evenly over the batter, gently pressing it in slightly. Bake for 1 hour, or until a toothpick inserted in the center comes out clean. Cool in the pan for 15 minutes, then transfer to a wire rack to cool completely.