Preheat the oven to 375 degrees F (190 degrees C).
Unroll the pizza dough onto a greased baking sheet. Press out to cover the entire sheet. In a medium bowl, mix together the sour cream, cream cheese and dill until smooth. Spread evenly over the crust.
Heat the olive oil in a skillet over medium heat. Add the onion, mushrooms, garlic and red bell pepper; cook and stir until onion is tender but the pepper is still crisp, about 4 minutes. Stir in baby spinach at the end of cooking. Spread this mixture over the top of the pizza.
Bake for 15 minutes in the preheated oven, or until the crust is golden at the edges. Cut into squares to serve.
