Bring a large pot of salted water to boil. Add the broccolini; cover and cook for 5 to 6 minutes, or until bright green and slightly tender.
In a large skillet, melt the butter. Add the lemon slices, and gently cook them over medium-high heat about 3 minutes per side (until the lemons are soft and slightly browned).
Return the drained broccolini to the pot. Add the broth and crushed red pepper; toss gently to coat. Transfer the broccolini mixture to a serving platter. Top with the lemons, green onions and salt.