In a small bowl, combine 1/2 cup all-purpose flour, 1/4 cup light brown sugar, and 1/2 tsp ground cinnamon. Add 1/4 cup cold butter pieces. Using your fingertips or a pastry blender, cut the butter into the flour mixture until coarse crumbs form. Set aside.

Preheat oven to 400°F (200°C). Line a standard 12-cup muffin tin with paper liners.

In a medium mixing bowl, whisk together 2 cups all-purpose flour, 1 tbsp baking powder, and 1/2 tsp salt. Set aside.

In a large mixing bowl, whisk together 1/2 cup melted butter and 1 cup granulated sugar until well combined. Beat in the 2 large eggs one at a time, mixing well after each addition. Stir in 1 tsp vanilla extract.

Gradually add the dry ingredients to the wet ingredients, alternating with 1 cup buttermilk, beginning and ending with the dry ingredients (e.g., 1/3 dry, 1/2 buttermilk, 1/3 dry, 1/2 buttermilk, 1/3 dry). Mix until just combined. Be careful not to overmix; a few lumps are okay.

Divide the muffin batter evenly among the 12 prepared muffin cups, filling each about two-thirds full.

Drop small dollops (about 1 teaspoon each) of 1/2 cup cranberry sauce over the batter in each muffin cup. Use a small spoon or knife to gently swirl the cranberry sauce into the batter, creating a marbled effect.

Generously sprinkle the prepared streusel topping over the top of each muffin.

Bake for 5 minutes at 400°F (200°C), then reduce the oven temperature to 375°F (190°C) and continue baking for another 15-17 minutes, or until a wooden skewer inserted into the center of a muffin comes out clean. The tops should be golden brown.

Let the muffins cool in the muffin tin for 5 minutes before transferring them to a wire rack to cool completely.