Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 9×13 inch baking pan.
Cream together the butter and sugar until light and fluffy. Beat in the eggs, one at a time, until thoroughly combined.
In a separate bowl, sift together the flour, baking soda, and salt. Add the flour mixture to the creamed butter mixture, alternating with the sour cream, and stirring until just combined. Stir in the vanilla extract.
Spread the batter into the prepared baking pan.
In a small bowl, mix together the pecans, brown sugar, and cinnamon. Sprinkle the mixture over the top of the batter.
Bake in preheated oven for 45 minutes, or until a toothpick inserted into the center of the cake comes out clean.
Allow to cool before serving.
Interesting Facts
Coffee cake is traditionally served in the morning with coffee.
Streusel is a crumbly topping made with butter, sugar, and sometimes spices.
Sour cream helps to keep the cake moist and adds a subtle tangy flavor.