Combine onions and water in a pot and heat high heat until water boils; strain and let cool.
Cut tips off of onions and take off peel.
Add shelled peas and 1 cup water to pot and let boil, covered over medium heat for 2 minutes. Mix in sugar snap peas and Chinese peas. Place lid on pot and cook 2 to 4 minutes or until crisp tender. Strain.
Heat butter until melted; stir into rosemary and onions. Reduce heat to low and stir in pea mixture and cook 2 to 3 minutes. Season with salt and pepper.