1. Rinse tomatoes. Pull off stems. Using sharp knife, cut out cone-shaped core from stem ends. Spoon out center of each, using small spoon. Drain upside down on paper toweling.
2. Bring a saucepan of water to boiling. Add broccoli; boil 5 minutes or until tender. Drain; let cool slightly. Combine broccoli and sour cream in food processor. Whirl to puree.
3. Heat oil in nonstick skillet over low heat. Add onion; saute for 3 minutes. Add flour; cook, stirring, 2 minutes. Add puree to skillet; cook 2 minutes, until thickened. Remove from heat. Stir in salt, cayenne and black pepper. Cool slightly. Stir in Parmesan. Spoon mixture into pastry bag fitted with large plain tip; pipe into tomatoes. Or use a spoon. Makes 36.