Pre-heat oven to 375 F.

Blueberry Reduction-

Place blueberries, sugar, and lemon juice in a small saucepan over medium low heat. Stir and smoosh blueberries with a spoon every minute or two till mixture is reduced to about ¼ of a cup. About 15 minutes. Let cool for about 10 minutes.

Topping-

Combine sugar and lemon juice in a small bowl. Add flour and butter and mix till crumbly. Set aside.

Muffins-

In a medium mixing bowl combine together flour, sugar, salt, and baking powder. Add in blueberries and gently mix again.

In a separate bowl whisk together eggs, vanilla extract, buttermilk, and oil. Slowly pour in, while whisking, the cooled butter.

Pour liquid mixture into flour mixture and stir with a large spoon till a few flour streaks remain. Do not overmix!

Assembly-

Spray a standard size muffin tin with cooking spray. Evenly distribute mixture into 12 portions of a muffin tin. Muffins will be filled fairly high. Add 1 teaspoon of reduction on top in the middle of each muffin and swirl in a figure 8 motion. Add about 1 ½ tablespoons of the topping to each muffin.

Bake for about 18-20 minutes till an inserted toothpick comes out with a few moist crumbs.

Let cool for 10 minutes in tin before removing muffins to finish cooling on a wire rack.