Add 2 tablespoons of the butter to a large nonstick skillet over medium heat. Add the broccolini and cook, tossing, for 1 minute.
Zest the lemon and add the zest to the skillet. Add the soy sauce and the remaining tablespoon butter and toss to coat. Halve the lemon and squeeze the juice in; continue tossing the broccolini until the tips of the broccolini begin to brown and the stalks are slightly tender, about 3 minutes.
Serve with the Alfredo Dipping Sauce.
Alfredo Dipping Sauce:
Warm the butter and cream in a saucepan or skillet until it starts to gently bubble around the edges, then add the cheese and pepper. Whisk until the cheese has completely melted, then transfer to a serving bowl.