Mix together the ricotta cheese, cooked spinach, parmesan, lemon zest, salt and pepper.
Beat the egg in a small bowl.
Lay out the wonton wrappers on the counter. Use your finger to spread the egg around the edges of the wonton wrappers (working in batches).
Add a teaspoon of filling to the center of each wonton wrapper.
Fold the wonton wrapper in half from corner to corner and then seal by pressing the edges together. Be sure to press out as much air as possible so the ravioli don't open up while cooking. Repeat with all wonton wrappers
Bring a large pot of salted water to a boil.
Bring the water down to a simmer, and add in the ravioli. Once the ravioli begins to float, after about 3 minutes, remove the ravioli from the pot with a slotted spoon and place on a platter.
Meanwhile, melt the butter in a saucepan over low heat.
Once melted and bubbles begin to form, add the garlic and sage leaves to the pan and continue to stir gently until the butter begins to brown.
Spoon the sauce over the ravioli and serve immediately.