Make the streusel by combining flour, sugar, and lemon zest. Cut in butter until crumbly.
Prepare the batter: Whisk together flour, baking powder, and salt. In a separate bowl, mix melted butter and sugar, then add yogurt, eggs, lemon zest, juice, and extracts. Blend in dry ingredients alternately with buttermilk, fold in blueberries last.
Assemble: Scoop batter into lined muffin tins, top with streusel, and bake at 370°F for 23-27 minutes until golden.
