Whisk together the granulated sugar, butter, sour cream, vanilla, and the egg.
Add the flour, baking powder, salt, cinnamon, and cardamom and stir just until combined. The batter will be thick. Fold in the peaches.
Pour mixture into a 9 x 9 inch baking pan that has been sprayed with non-stick spray.
Mix together all the ingredients for the crumb topping, and spread over top of the coffee cake.
Bake in a 350-degree oven for 35 – 45 minutes, or until a toothpick comes out clean when poked in the middle. The crumb topping will also be a nice golden brown.
Cool slightly, serve.
Both Greek yogurt and sour cream work well in this recipe.If the peaches are not juicy, you may want to cut back the flour just a little.I have also made this in an 8″ springform pan. Very nice presentation, but it does take a little bit longer to bake.