I love the flavor of sweet strawberries balanced with the amazing tang of buttermilk. That being said, I think you could add any other berry, or even head over to stone fruit territory, like peaches and a hint of cinnamon, or apricots and almond. Maybe nectarines and rosemary scented sugar (rub chopped rosemary needles into the sugar with your hands) would be a nice option as well.
Preheat oven to 350. Butter a 10-inch cake pan or pie plate.
Mix flour, baking powder and salt together in a small bowl. In a larger bowl, beat butter and 3/4 cup sugar until pale and fluffy with an electric mixer, about 3 minutes. Mix in egg, buttermilk and vanilla until just combined. Add dry mixture gradually, mixing until just smooth.
Spread into prepared pie plate. Arrange strawberries on top of batter in a single layer. Sprinkle remaining 3 tablespoons sugar over berries.
Bake cake for 10 minutes then reduce oven temperature to 325°F and bake cake until golden brown and a toothpick comes out free of wet batter, about 50 minutes. Some of the top will continue to look gooey from the fruit, so its best to test in a non fruit covered section to see if the toothpick comes out clean. Let cool in pan on a rack, and serve warm or at room temp with whipped cream, ice cream or simply as is.