• Preheat your oven to 400°F (200°C) and line a standard muffin or cupcake pan with paper liners. Set aside.

Prepare the Streusel Topping:

• In a small bowl, whisk together the flour, granulated sugar, and cinnamon.
• Add the melted butter and stir with a fork until the mixture becomes crumbly. Refrigerate until ready to use.

Make the Muffin Batter:

• In a large bowl, stir together the flour, baking powder, and salt. Set aside.
• In a medium bowl, combine the granulated sugar and lemon zest. Rub the mixture together for about a minute to release the lemon oils.
• Add the eggs to the sugar-zest mixture and whisk until well combined.
• Mix in the Greek yogurt, vegetable oil, vanilla extract, and fresh lemon juice until the mixture is pale and yellow.

Combine Wet and Dry Ingredients:

• Fold the wet ingredients into the dry ingredients until just combined. Be careful not to overmix.
• In a separate small bowl, toss the blueberries with 1 tablespoon of flour until they're coated. Gently fold the flour-coated blueberries into the batter.

Assemble and Bake:

• Spoon the batter into the prepared muffin tins, filling each cup about two-thirds full.
• Top the batter with the reserved blueberries and generously sprinkle the streusel topping over the blueberries.
• Bake in the preheated oven for 5 minutes, then reduce the temperature to 375°F (190°C) and continue baking for 13-15 minutes, or until a toothpick inserted into the center of a muffin comes out clean.

Cool and Serve:

• Allow the muffins to cool in the pan for 5 minutes, then transfer them to a wire rack to cool completely.
• Serve warm or at room temperature, and enjoy!