Turn the broiler to high.
Remove the husks from the tomatillos and rinse the sticky residue off the skins. Slice the tomatillos in half from top to bottom, removing stems as necessary. Place on large baking sheet, cut side up.
Slice jalapeno pepper in half. Remove the seeds and membranes from the inside of the pepper for a milder salsa. Leave seeds and membrane intact for a hotter salsa. Place 1 or both halves of the pepper on the baking sheet with the tomatillos, depending on how spicy you want it.
Place the whole poblano on the baking sheet.
Cut the onion to large chunks and scatter over the baking sheet.
Broil for 10-15 minutes or until charred. Place the poblano pepper in a ziploc or paper bag and seal. Let sit for 10 minutes to steam. Remove from the bag carefully and peel the skin from the pepper.
Add the tomatillos, jalapeno, poblano, onion, cilantro, lime juice, and salt to a food processor or blender and process until smooth.
Cool before serving.
Store covered in the fridge for up to 1 week.