Preheat oven to 375 degrees. Line a baking sheet with aluminum foil or parchment paper. Slice the tomatillos in half and place face down on the baking sheet. Add the onion (sliced in quarters), garlic and jalapeno. Bake for 15 minutes. Change the heat to broil on high, and broil the vegetables for 5 more minutes or until nice and brown.
Remove the vegetables and add everything to a blender. Blend on high until everything is combined and there are no chunks. Add the salt, pepper, cumin, sugar, lemon, and cilantro. Blend. Taste and adjust spices accordingly (sometimes you may need some more salt or cumin).
Transfer to a glass container and let it cool completely. Cover and place in the fridge for up to one week. Serve with chips and salsa! Or pour over your own tacos.
* Remove the papery skin off the tomatillos and then rinse them under some cold water to remove the stickiness.
** You may need to adjust the salt as required. I sometimes add a bit more salt and a bit more cumin for a nice flavour. It is up to your discretion!