Cucumber Salad with Smoked Salmon
1 (3 ounce) package smoked salmon, flaked 1 cup light sour cream 1 cup plain Greek yogurt 1 shallot, minced 2 large cucumbers, peeled and sliced 2 tablespoons capers, chopped 2 tablespoons chopped fresh dill, or to taste 2 tomatoes, sliced salt and black pepper to taste ½ lemon, juiced ½ teaspoon white vinegar, or to taste