Turn your oven to 420 degrees. Dry the chicken with a couple of paper towels.
In a small bowl, mix the butter, 2 tablespoons of the parmesan cheese, parsley, paprika, garlic, salt, and pepper.
Using your fingers or a spoon, carefully separate the skin from breast meat and as much as possible on the legs. Tuck half of the parmesan butter under the skin and spread the rest on top.
Place the onion and lemon slices in the bottom of a small roasting pan or heavy-bottomed, ovenproof pot and place the chicken on top.
Roast for 45 minutes then turn the heat down to 350 degrees and roast for another 45 minutes. Sprinkle the remaining tablespoon of parmesan cheese on top of the chicken and pop it back in the oven for 5 more minutes.
Let the chicken rest of 10 minutes before carving it. Pour the juice at the bottom of the roasting pan into a bowl and serve it on the side to pour over the chicken.