Onion parmesan toast is a quick and easy appetizer and a great starter recipe for any party or dinner. This parmesan cheese toast with onion is prepared by spreading a mixture of mayonnaise and chopped onion on grilled bread. Grated Parmesan cheese and onion mixture is spread on toasted bread and is topped with butter. This is then microwaved till cheese starts bubbling. Garnish with oregano/Italian seasoning and serve immediately.