1 yellow onion, sliced into slivers, lengthwise (with the grain)
1 large bunch of raw broccoli rabe (raab, rapini), rinsed and cut into 2-inch long pieces
2-3 garlic cloves, sliced
1/4 teaspoon red chili flakes
Heat 2 Tbsp olive oil in a large sauté pan on medium heat. Add the onions, spread out in a thin layer.
Cook, stirring occasionally until softened and then lightly browned.
(Tip: to speed up the caramelization process you can sprinkle a pinch of sugar over the onions.)
If the onions start to dry out at all, lower the heat (you can add a little water to them too.) They should brown, but not get dried out.
After you start the onions, bring a large pot of water to a boil.
The onions take at least 15 minute to cook, so you’ll have time to get the water boiling.
Salt the water (about a tablespoon of salt for 3 quarts of water).
Prepare an ice bath, fill a large bowl half way with ice water. Add the rabe to the boiling water.
Blanch for 1 minute.
Use a slotted spoon to remove from the boiling water and put in the ice bath to stop the cooking. Shocking the rabe with ice water will also help keep the rabe bright green colored.
Once the onions are lightly browned, remove them from the pan to a bowl.
Using the same pan, add another Tbsp of olive oil and heat the pan on high heat. Add the chili flakes. Once the chili flakes start to sizzle, add the garlic.
Once the garlic just starts to brown at the edges add the broccoli rabe and the onions.
Toss the rabe mixture so that it gets well coated with the olive oil.
Cook on high heat until most of the moisture is gone, about 5 minutes if you blanched first, a minute or too longer if you skipped the blanching.