To prepare basil sauce, cook 1 cup basil leaves in boiling water 15 seconds; drain. Plunge basil into ice water; drain and pat dry. Combine basil and broth in a blender; process until smooth. Let mixture stand 2 hours at room temperature. Strain through a fine sieve into a bowl; discard solids. Add vinegar and salt, stirring with a whisk.
To prepare salad, arrange yellow and red tomato slices alternately on a large platter. Drizzle with basil sauce; sprinkle with cheese and pepper. Top with 1/2 cup sliced basil. Serve immediately.