Lightly oil the bottom of a small baking dish (I used a 6 inch by 6 inch, a little smaller is fine too).
If ricotta is wet and milky, use a cheesecloth to drain out excess liquid. Spread ricotta thinly onto the bottom of your baking dish, top with a little olive oil, and bake until cheese has begun to set and is brown on top. This may range anywhere from 20-40 minutes, depending on how wet your cheese is to start with.
When ricotta starts to brown, top with breadcrumbs and bake for an additional 10 minutes, until breadcrumbs are nice and toasty.
Meanwhile, melt butter in a small saucepan over medium heat. Stir in onion, garlic, and sage and cook until softened, about 3 minutes.
Stir in peas, ½ cup of water, and lemon zest. Simmer until peas are a bright green color and liquid has reduced some, about 5 minutes. Season with salt and pepper to taste.
When ricotta is done baking, top with peas and sauce. Sprinkle Parmesan on top as garnish.
Recipe by Things I Made Today at https://www.thingsimadetoday.com/2015/04/28/baked-ricotta-with-peas/