Preheat the oven to 375°F and spray a baking dish with cooking spray.
Chop the pistachios into small pieces. Alternatively, crush them using a mallet or rolling pin.
Add the pistachios to the brown sugar and cinnamon in a medium bowl. Mix everything together well until it is a sandy texture. Set this aside.
Wash and gently pat the peaches dry. Halve the peaches and remove the pit. Cut a small disk from the curved side of each peach half so that it will sit flat in the baking dish.
Lay out the peaches in a single layer on the baking dish. Add a generous tablespoon of sour cream to each half, spreading it out to the edges of the peaches.
Divide the brown sugar mixture among the peaches, covering the sour cream. You may have a bit extra, depending on the size of your peaches.
Bake the peaches for 20-25 minutes, until the peaches are soft and the topping is golden. Serve warm.
Nutrition facts are sometimes provided below and are calculated using an online calculator. With specific brands of ingredients and additions, omissions, or substitutions the nutrition facts may change. We encourage you to use your own nutrition facts calculator to obtain the most accurate nutrition facts for your meal.