Melt 2 tablespoons of the butter in a large skillet over medium heat. Add the onion and cook for 3 minutes.
Add the rice and cook, stirring constantly, for 1 minute. Reduce heat, add the wine, and cook, stirring frequently, until the liquid is absorbed.
Add the broth ½ cup at a time, stirring occasionally and waiting until it’s absorbed before adding more. This should take about 30 minutes total. The rice should be tender but still slightly firm. Remove from heat.
Add the lemon juice, ½ teaspoon salt, ¼ teaspoon pepper, Parmesan, and the remaining butter and stir until the butter melts.
Spoon into individual bowls and sprinkle with the zest and parsley.