Preheat and Prepare Pan. Preheat the oven to 400°F/204°C. Line a medium-sized muffin pan with 12 cupcake liners or grease the bottoms of each muffin cup.
Make the Streusel Topping. In a small bowl mix together the light brown sugar, granulated white sugar, flour, and lemon zest with a fork. Cut in the butter until the mixture looks like medium-grain rice. Set aside for later.
Sift Dry Ingredients. Sift together flour, baking powder, baking soda, and salt into a large-sized bowl. Set aside.
2 Cups All-Purpose Flour, 2 Teaspoons Baking Powder, ½ Teaspoons Salt, ½ Teaspoon Baking Soda
Combine Wet Ingredients. In a medium-sized bowl beat together the oil, white sugar, egg, milk, and lemon zest with a fork or whisk.
½ Cup Cooking Oil, ¾ Cup Granulated White Sugar, 1 Large Egg, ½ Cup Whole Milk, 1 Tablespoon Lemon Zest
Mix Wet into Dry Ingredients. Add the wet ingredients all at once into the dry ingredients. Using a spoon or a rubber spatula, gently fold the wet ingredients into the dry ingredients, but stir only until the batter is barely mixed. Streaks and clumps of flour/dough should still be visible.
Fold in Blueberries. Gently fold the blueberries into the batter.
1 ½ Cups Blueberries
Fill Baking Cups. Spoon the batter into the prepared baking cups ¾ full and sprinkle with the streusel topping.
Bake. Bake in the preheated oven for 25 to 28 minutes or until a toothpick inserted in the middle of a muffin comes out clean and the tops are slightly golden brown. Remove the pan from the oven and let the muffins cool for 10 minutes in the pan before removing and transferring them to a wire rack to cool completely.Serve and Enjoy!
Notes
My Top Tips♡ Cold crumb toppings work best. Put the streusel crumb topping in the refrigerator, as you mix the muffin batter, if your kitchen is warm.♡ All ingredients should be at room temperature unless otherwise noted.♡ Since the batter will continue to mix as the blueberries are added, it is important not to overmix the batter before adding the blueberries.Make-Ahead, Storage & ReheatingMake-Ahead: These blueberry muffins are best eaten the day they are baked.Storage: They can be stored in an airtight container for up to 3 days.Reheating: Gently warming the muffins in the oven or microwave will bring out the flavor.