Preheat oven to 350º. Line a baking pan with paper liners, or grease with cooking spray.
Prepare the crumble topping by whisking the ingredients together in a small bowl and set to the side.
In another small mixing bowl, toss blueberries with 3 Tbsp. gluten free flour until blueberries are coated. Set aside.
In a large mixing bowl (or an electric stand mixer), beat together butter (or dairy free substitute) and sugar until light and fluffy. Add eggs, vanilla, milk, lemon juice, lemon zest, and continue beating until smooth.
Mix in Gluten Free flour mixture, baking powder, & salt until just combined.
Finally, Carefully fold in blueberries.
Fill muffin cups about 3/4 full of batter. Sprinkle each cup of batter with about 1 Tbsp.
Bake at 350º for 20 to 25 min, until a toothpick inserted into the center of a muffin comes out clean.
Let muffins cool for a few minutes in the muffin pan before removing to cool on a wire rack. Serve immediately. Store uneaten muffins in an airtight container. Or Freeze for up to 3 months.
Use a dairy free milk and dairy free butter substitute.