Preheat your oven to 350°F. Grease and flour a 9x5-inch loaf pan or line with parchment paper.

In a small bowl, mix together pecans, brown sugar, granulated sugar, and flour. Cut in the cold butter with a fork or your fingers until the mixture resembles coarse crumbs. Set aside.

In a medium bowl, whisk together flour, baking powder, baking soda, cinnamon, and salt. Set aside.

In a large bowl, cream the softened butter and sugar until light and fluffy (about 2–3 minutes). Beat in the eggs one at a time, then stir in the vanilla.

Add the flour mixture in 2 parts, alternating with the buttermilk. Mix just until combined. Do not overmix.

Gently fold in the diced peaches.

Pour half the batter into the prepared loaf pan. Sprinkle with half the praline crumb mixture. Add the remaining batter on top, and finish with the rest of the crumb topping.

Bake for 55–65 minutes, or until a toothpick inserted into the center comes out clean.

Let the cake cool in the pan for 15–20 minutes, then transfer to a wire rack to cool completely.