Apple Cinnamon Streusel Loaf

Preheat oven to $350^\circ\text{F}$ ($175^\circ\text{C}$). Grease an $8.5\times4.5$-inch loaf pan and line with parchment paper. In a small bowl, whisk $\frac{1}{2}$ cup flour, $\frac{1}{4}$ cup granulated sugar, $\frac{1}{4}$ cup brown sugar, and 1 tsp cinnamon. Cut in $\frac{1}{4}$ cup cold, cubed butter using a pastry cutter or fork until coarse crumbs form. Set aside.

In a medium bowl, whisk together $1\frac{1}{2}$ cups flour, 1 tsp baking powder, $\frac{1}{2}$ tsp baking soda, $\frac{1}{2}$ tsp salt, 1 tsp cinnamon, and $\frac{1}{2}$ tsp nutmeg.

In a large bowl, beat $\frac{1}{2}$ cup softened butter, $\frac{1}{2}$ cup granulated sugar, and $\frac{1}{2}$ cup brown sugar on medium speed for 2–3 minutes until fluffy. Beat in 2 eggs one at a time, then stir in 1 tsp vanilla extract.

Gradually add the flour mixture and $\frac{1}{2}$ cup sour cream (or Greek yogurt) to the wet ingredients in alternating batches, starting and ending with flour. Mix until just combined. Gently fold in $1\frac{1}{2}$ cups diced apples.

Spread half the batter into the pan and sprinkle with half the streusel. Top with remaining batter and rest of the streusel. Bake for 50 to 60 minutes until a toothpick inserted in the center comes out clean. Cool in the pan for 15 minutes before transferring to a wire rack.