Blanch it, shock it in ice water, then squeeze out the extra water.
In a large pot, olive oil and garlic. Cook the garlic till its golden. Add chili flakes, add the broccoli rabe. Sauté for a few minutes. Salt and pepper. Lemon zest. Taste it and adjust as necessary. Serve and enjoy.
This technique gets you broccoli rabe that's green, vibrant, and tender. No more soft, gray, mushy broccoli rabe.