There are a few different ways you can slightly remove the bitter edge out of broccoli rabe. One way is to blanch it in boiling water for a few minutes before cooking it. This will help to remove some of the bitter compounds from the vegetable. You can also sauté the broccoli rabe in olive oil over medium-high heat until it's wilted and tender, which should take 5-7 minutes. Finally, acidity can also help balance the bitterness in broccoli rabe. Adding lemon juice or vinegar to the final rapini dish can brighten the flavors and make it palatable.