For the cake:
1 cup (2 sticks) salted butter, softened to room temp.
2 cups sugar
3 large eggs
1 tbsp vanilla extract
1/2 tbsp lemon extract
2 3/4 cups all-purpose flour
2 tsp baking powder
1/2 tsp baking soda
1/4 tsp salt
1 1/4 cup whole real buttermilk
1 pound fresh blueberries

For the crumble topping:
2 tbsp real butter, slightly softened
2 tbsp brown sugar
3 tbsp flour
2 tbsp oats, quick-cooking is fine

For the glaze:
1 cup powdered sugar
1 tsp lemon extract
2 tbsp milk