Whisk flour, 2 tablespoons sugar, baking powder, baking soda and salt together in bowl. In second bowl, whisk buttermilk, eggs, sour cream and melted butter together. Make well in center of flour mixture and pour in buttermilk mixture; gently stir until just combined (batter should remain lumpy, with few streaks of flour). Do not overmix. Let batter sit for 10 minutes (don’t skip this step). .
Combine strawberries, vanilla and remaining 1 tablespoon sugar in small bowl; set aside.
Heat 1 teaspoon oil in 12-inch nonstick skillet over medium heat until shimmering. Using paper towels, carefully wipe out oil, leaving thin film on bottom and sides of pan.
Using 1/4-cup dry measuring cup, portion 4 pancakes into pan. Cook until edges are set, first side is golden brown and bubbles on surface are just beginning to break, 2 to 3 minutes. Sprinkle 1 tablespoon strawberry mixture over each pancake.
Using wide spatula, flip pancakes and continue to cook until second side is golden brown, 1 to 2 minutes longer. Serve pancakes immediately or transfer to prepared rack in oven. Repeat with remaining batter and strawberry mixture, adding remaining 1 teaspoon oil, as needed.