Press Sauté; melt butter in Instant Pot®. Add onions; cook 15 minutes, stirring occasionally. Add sugar, salt and pepper; cook and stir 5 to 7 minutes or until onions are golden brown. Add wine; cook and stir 1 minute or until evaporated. Stir in broth; mix well. Secure lid and move pressure release valve to Sealing position. Press Manual or Pressure Cook; cook at high pressure 5 minutes. When cooking is complete, press Cancel and use quick release. Preheat broiler. Ladle soup into individual ovenproof bowls; top with 1 or 2 slices bread and about 2 tablespoons cheese. Place bowls on large baking sheet. Broil 1 to 2 minutes or until bread is toasted and cheese is melted and browned.