Chop off most of the rabe stem close to where the leaves begin. (now that is a personal preference and feel free to do otherwise. I don't like having that much stem in my dish)

Wash the rabe. I wash each leaf separately but for those of you not so anal about it, fill your sink up with water and place the leaves in there. Swirl the leaves pretty vigorously for a few seconds and then place in a spinner to dry.

Once the rabe has been spun, its chopping time. I usually grab a bunch of leaves just enough to fit in my hand so that my fingers and thumb barely touch. Then I slice on my cutting mat. I tend to like thinner slices. But feel free to cut your preferred size. Set aside.

Next heat, on high heat, 2 tbsp of oil in a large pot until it starts to smoke. Carefully drop the chopped rabe into the pot. Please be careful as you are adding water drops to very hot oil. Of note, depending on the size of pot and the size of your rabe bunches, you may have to add them to the pot in batches. It may splatter as you will be adding wet rabe to hot oil. After about 5 seconds stir the rabe so that what was on the Bottom ends on the top. As it starts to cook, it will reduce in volume. Continue to add the rabe until it is all in the pot.

Add about 1/2 tsp of salt and continue to cook until the rabe is a fraction of its original amount and is still dark green in color. You will soon see a build up of the rabe liquid in the pot.

Remove the pot from the stove and drain the rabe liquid. Place the rabe in a mixing bowl and set aside.

Wipe down the inside of the same pot and add the remaining 2 tbsp of oil. Heat the oil on medium. Add the onion and saute until softened. Add about 1/8 tsp of salt once the onion has softened. Continue to cook for another 2 minutes.

Add the tomatoes and cook until most of the tomato liquid has dissipated. Add a couple pinches of salt and continue to cook for another 2 to 3 minutes. You are ready for the next step when the tomatoes no longer look or taste raw.

Add the broccoli rabe to the onion and tomatoes. From this moment on, you can cook the combined mixture for 3 minutes, which is usually about enough time for the mixture to combine and merge its flavors or longer, which I find tends to rob the rabe of its bitterness. So play around with the cooking times until you come by your preferred taste. Since I love the bitterness, I tend to cook everything closer to the 3 minute mark.