To make the topping, place 1/4 cup butter and caramels in a microwave-safe bowl. Heat at half power for 2 minutes, then stir. If mixture is not smooth, heat at half power in 30-second increments until melted and smooth when stirred. Set aside to cool for about 5 minutes.

Combine flour, brown sugar, pecans, and salt. Add cooled caramel mixture and mix with a fork until crumbly. Set aside.

To make the cake, preheat oven to 350°. Grease a 9-inch square baking pan.

Whisk together flour, baking powder, baking soda, salt, and cinnamon. Using an electric mixer on medium speed, beat butter, sugar, and brown sugar until light and fluffy. Add eggs, one at a time, mixing well after each addition. Reduce mixer speed to low. Add sour cream and vanilla, mixing just until combined. Add flour about 1/2 cup at a time, and mix just until combined.

Transfer half of the batter to prepared pan and spread evenly. Sprinkle with half of the topping mixture. Drop remaining batter on top and spread gently. Sprinkle with remaining topping mixture.

Bake 50 to 55 minutes, or until a pick inserted into the center comes out clean. Cool in pan for 15 minutes before serving.