Blueberry with crumble muffin

Name: Blueberry with crumble muffin
Prep time: 15 min
Cook time: 30 min
Total time: 45 min
Cuisine: European, American, British
Ingredients: FOR THE STREUSEL CRUMB TOPPING:; 1/2 cup all-purpose flour (72g); 1/2 cup sugar (112g); 1/2 tsp ground cinnamon; 1/4 cup butter melted (salted or unsalted both work); 1.5 cups all-purpose flour (212g); 3/4 cup granulated sugar; 2 tsp baking powder; 1/4 tsp kosher salt; Zest of 2 meyer lemons (or do zest of 1 orange plus zest of 1 lemon); 1/3 cup unsalted butter melted (about 5.33 tbsp); 1 large egg; 2/3 cup buttermilk; 2 cups blueberries (I use frozen)