In large serving bowl combine tomatoes, red onion, and yellow sweet pepper. In screw-top jar combine 1/4 cup olive oil, the red wine vinegar, mustard, Italian seasoning, 1/2 teaspoon salt, and 1/4 teaspoon black pepper. Cover; shake well to combine. Add to tomato mixture and stir to coat. Cover and refrigerate overnight (up to 24 hours).
Preheat oven to 400 degrees F. In a shallow baking pan, toss bread cubes with 1 tablespoon olive oil to coat. Bake about 10 minutes or until toasted, stirring once. Remove and cool on pan. Add bread cubes and basil to tomato mixture; toss to coat. Top with shaved white cheddar cheese. Makes 6 to 8 servings.