Preheat oven to 400 degrees. Coat a muffin tin with non-stick cooking spray. Use a pastry brush to evenly coat the tin cups.
In a small saucepan, combine 1 cup blueberries and 1 tsp sugar. Bring to a boil and reduce to a simmer. Stir occasionally using the back of a spoon to mash some of the berries. Stir until sauce is thickened, about 5-6 minutes. Let cool for 5-10 minutes.
In a large bowl, combine flour, lemon zest, baking powder and salt. Whisk to combine.
In another bowl, combine eggs, sugar, buttermilk, oil, melted butter, and vanilla. Whisk together.
Pour wet mixture over dry and stir gently with spatula, or wooden spoon, just until combined. Do not over mix. Fold in 1 cup blueberries
Scoop a small amount of batter into each muffin tin--about 1/3 full. Evenly divide blueberry jam between the 12 cups. Use a small knife or spoon to gently swirl jam into batter. Continue dividing batter between each tin. Cups will be full. Add additional blueberries to any cups that need a few. Sprinkle with turbinado or granulated sugar.
Bake for 15-18 minutes until toothpick inserted in center comes out clean.
Remove from oven and cool in the pan for 5 minutes. Using a small knife loosen the top of each muffin from the sides of the pan. Flip out of pan and cool on wire rack for 5 minutes.