Heat oil in a large Dutch oven over medium-high heat. Add onion, salt, and garlic; sauté 4 minutes. Stir in tomato; cook 8 minutes, stirring occasionally. Stir in 3 cups water, wine, and clam juice; bring to a boil. Reduce heat, and simmer 6 minutes.
Add clams to pan. Cover and cook 10 minutes or until clams open; discard any unopened shells. Remove from heat. Stir in parsley, oregano, and lemon juice. Place 1/2 cup pasta in each of 6 soup bowls; ladle 5 clams and about 1 cup broth over each serving. Top each serving with 1 tablespoon cheese.