Vegetarian Borscht

Name: Vegetarian Borscht
Ingredients: 3 tablespoons extra-virgin olive oil; 2 medium russet potatoes, peeled and cut into 1/2-inch cubes; 2 medium carrots, peeled and cut into 1/2-inch pieces; 2 small leeks, halved lengthwise and sliced (white and light green parts only); 1/2 small savoy cabbage, cored and chopped; Kosher salt and freshly ground pepper; 3 medium beets with greens, scrubbed; 1 tablespoon tomato paste; 2 cloves garlic, chopped; 2 tablespoons fresh lemon juice; Sour cream and/or chopped fresh dill, for topping; Sliced pumpernickel bread, for serving