Preheat oven to 350°F (180°C). Grease an 9-inch pie dish or 8x8 inch square pan or 7x9 inch rectangular pan. Add 2 cups blueberries to the dish.
In a bowl, add ¾ cup sugar and the grated zest of 1 lemon. Mix with a spoon. Add ⅓ cup melted butter (or olive oil), ½ cup Greek yogurt, and 1 large egg. Whisk until smooth.
Add 1 cup all-purpose flour, 1 teaspoon baking powder, and ½ teaspoon kosher salt. Stir until just combined. Fold in the remaining 0.5 cups blueberries.
Spoon the batter over the blueberries. Spread gently. Sprinkle 1 tablespoon sugar on top.
Bake for 35–40 minutes. 35 super gooey center, 40 minutes firmer still very moist. The edges should look set and lightly golden. The center should be soft, but not wet. Let cool for 5–10 minutes. Serve warm with a spoon.
