Optional: Salad croutons and grated Parmesan cheese
Select saute setting on a 6-qt. electric pressure cooker and adjust for medium heat; add butter. Add onion; cook and stir until tender, 6-8 minutes. Add garlic and sugar; cook 6 minutes longer. Stir in stocks, wine and salt. Press cancel. Lock lid; close pressure-release valve. Adjust to pressure-cook on high for 8 minutes.
Let pressure naturally release for 3 minutes; quick-release any remaining pressure. If desired, serve with croutons and Parmesan cheese.