Prepare Dill Cream by combining sour cream, dill, onion and lemon juice in a small bowl.
On a lightly floured surface, roll the dough out into a 10-inch round. Transfer dough to a rimless baking sheet; brush with olive oil. Scatter sliced onion over the top. Bake until crust is golden brown, 6 to 8 minutes. Let cool 5 minutes.
Spread the Dill Cream over the top to within an inch of the edge. Arrange the salmon to cover the surface entirely. Use a pizza wheel to slice into 6 pieces.