Note: The original directions appear incomplete, so the steps below are reconstructed from the ingredient list and standard quick-bread preparation methods.

Preheat oven to 350°F (175°C). Grease and line a loaf pan with parchment paper.
In a large mixing bowl, cream together the butter and 1 1/4 cups sugar until light and fluffy.
Beat in the sour cream, lemon zest, vanilla extract, and eggs until fully combined.
In a separate bowl, whisk together the flour, baking powder, salt, and cardamom.
Gradually add the dry ingredients to the wet ingredients and mix just until combined.
Fold in the diced rhubarb.
Transfer the batter to the prepared loaf pan and smooth the top.
Arrange the sliced rhubarb over the surface and sprinkle with the remaining 2 tablespoons sugar.
Bake for 55–65 minutes, or until a toothpick inserted into the center comes out clean.
Allow the bread to cool in the pan for 10–15 minutes before transferring to a wire rack to cool completely.
Slice and serve.