Bring a large pot of salted water to a boil. Meanwhile, in a large skillet, heat olive oil with garlic over medium heat until garlic just begins to turn golden, about 2 minutes. Add red pepper flakes and toast for about 30 seconds. Remove from heat.

Add broccoli rabe to boiling water and cook until thickest parts of stalks are tender, 2 to 3 minutes. Drain well. Add rabe to skillet, toss well, and return to medium-high heat. Cook, stirring occasionally and lowering heat as necessary to prevent scorching, until rabe is very tender, about 10 minutes. Season with salt. Serve right away, or continue to cook over low heat, stirring occasionally, for up to 20 minutes longer before serving (it just gets better and better).