This is a classic sour cream coffee cake, delicious plain or garnished with berries, stone fruit, or pears. Blueberries add sweetness and healthy antioxidants.
Position a rack in the lower third of the oven and preheat to 350 F. Butter a 9-inch round or square baking pan and set aside.
To make the topping, combine the flour, sugar, cinnamon, and salt in a small bowl. Using your fingers or a pastry blender, cut in the butter until the mixture resembles coarse crumbs. Stir in the nuts and set aside.
Place the sugar and butter in the bowl of an electric mixer and beat on medium-high speed until the mixture is light and fluffy. Add the egg yolks, vanilla, lemon zest, and sour cream; mix on low speed until blended.
In a separate bowl, whisk together the flour, baking soda, baking powder, and salt. Add the dry mixture to the batter and mix until just combined. Don't overmix or the cake will be tough. Gently stir in the blueberries, being careful not to break them.
Spread half of the batter in the prepared pan and sprinkle with half of the topping mixture. Repeat.
Bake the cake until it's set and a toothpick inserted into the center comes out clean, 45 to 55 minutes. Cool in the pan on a wire rack at least 15 minutes before serving.