In a small bowl whisk together the flour, baking powder, baking soda, and salt. Set aside.
In a larger bowl cream together the 1/2 cup softened butter and 2/3 cup (granulated) sugar. Stir in the egg and vanilla extract. Stir in the flour mixture. Stir in the greek yogurt until just combined.
For the topping, stir together the pecans, brown sugar, cinnamon, salt, and three tablespoons softened butter.
In a lightly buttered loaf pan, pour in the batter. Spoon the topping mixture over the top of the batter (as in the photo above). Bake at 325°F for 45-50 minutes, until a tooth pick inserted in the center comes out clean. You’ll notice that a lot of the topping with end up at the bottom of the coffee cake.
Allow to cool for ten minutes before flipping the cake out of the pan (or you can serve it from the pan, either way).