Preheat your oven to 375°F (190°C) and line a muffin pan with muffin liners or paper liners.

In a large bowl, whisk together the flour mixture: all-purpose flour, baking powder, and sugar.

In a small bowl, combine the wet ingredients: greek yogurt, milk, eggs, unsalted butter, lemon juice(or lemon zest). Mix until smooth.

Pour the wet mixture into the dry ingredients and stir until combined. Be careful not to overmix; the batter should have a thick consistency. Gently fold in the fresh blueberries to keep them intact.

Making the delicious streusel: In a medium bowl, combine unsalted butter, flour, and powdered sugar. Mix with a fork until the mixture becomes crumbly.

Divide the muffin batter evenly among the muffin cups, filling each about 3/4 full. Sprinkle the streusel topping generously over the top of the muffins before baking. Make sure the streusel mixture is crumbly and evenly distributed to ensure a crunchy, sweet topping.

Bake in the preheated oven for 15-20 minutes or until a toothpick inserted into the center of a muffin comes out clean. Let the muffins cool in the pan for 5 minutes before transferring them to a wire rack to cool completely. Enjoy!