Slow-Cooker Carnitas Tacos With Pickled Onions

For the carnitas:

bone-in pork shoulder (or 2 pounds boneless)

Kosher salt

dried oregano

ground cumin

neutral oil, such as grapeseed

yellow or white onion, quartered

garlic, peeled and smashed

jalapeño, stem removed and cut in half

The juice of 1 orange

The juice of 1 lime

For the quick-pickled onions:

medium red onion, sliced into 1/4-inch-thick half-moons

granulated sugar

kosher salt

rice vinegar, white wine vinegar, or apple cider vinegar

black peppercorns, optional

small springs thyme, optional

For the tacos:

Small corn tortillas, warmed

Chopped cilantro

lime, cut into 8 wedges