Follow these simple steps to create a flavorful Rhubarb Coffee Cake:

1. Preheat the Oven: Preheat your oven to 350°F (175°C). Grease and flour a 9×13 inch baking pan.

2. Mix Dry Ingredients: In a large mixing bowl, combine the flour, baking powder, baking soda, and salt. Whisk these together until well incorporated.

3. Cream Butter and Sugar: In another bowl, cream the softened butter and granulated sugar together until light and fluffy.

4. Add Egg and Yogurt: Beat in the egg, followed by the yogurt (or sour cream) and vanilla extract, mixing until just combined.

5. Combine Mixtures: Gradually add the dry ingredients to the wet mixture, stirring until the batter is smooth and everything is well combined.

6. Fold in Rhubarb: Gently fold the chopped rhubarb into the batter. If using, add chopped nuts for added texture.

7. Pour into Pan: Spread the batter evenly into the prepared baking pan.

8. Prepare Topping (optional): If you’d like, mix the brown sugar and cinnamon together. Sprinkle this mixture evenly over the top of the cake batter.

9. Bake: Place the pan in the preheated oven and bake for 40-45 minutes. The cake should be golden brown and a toothpick inserted in the center should come out clean.

10. Cool: Once done, remove the cake from the oven and let it cool in the pan for about 15-20 minutes. Then transfer to a wire rack to cool completely.