Heat oven to 350°F. Lightly grease the bottom and sides of an 8-by-4-inch loaf pan.

In a small bowl, combine rolled oats, brown sugar, cardamom and cinnamon. Cut in cold butter with a pastry cutter or fork until mixture resembles coarse crumbs. Place bowl in fridge while you prepare the bread.

In a large bowl, whisk sour cream, brown sugar, oil, vanilla and egg until smooth. In a separate large bowl or bowl of a stand mixer fitted with the paddle attachment, stir together flour, baking powder, baking soda, salt and cinnamon. Add sour cream mixture to flour mixture; stir until just combined. Fold in diced peaches.

Pour batter into prepared loaf pan. Top with sliced peaches and streusel. Bake 50 minutes to 1 hour until a toothpick inserted in the center comes out clean. Tent loaf with foil halfway through baking if peaches are drying out too much or top is browning too quickly.

Cool bread 10 minutes in pan, then carefully remove from pan. Transfer to a cooling rack to cool completely.