Brown & Season: Heat a skillet (or Instant Pot on sauté) over medium. Add ground beef and olive oil if needed. Cook 6-7 min, breaking into crumbles until browned. Drain excess fat, stir in taco seasoning, and cook 1 min more.
Cool Meat: Let the beef cool 10 min so steam won't wilt the greens.
Layer the Jars: Bottom (wet) — 2 Tbsp salsa. Middle (hearty) — ¼ beef, 2 Tbsp cheese. Top (dry) — ¼ cup lettuce, 2 Tbsp sour cream. Screw on lids. Keep upright up to 4 days in the fridge.
Grab & Go: Toss a chilled jar in your lunch bag with a fork. Shake to mix, then dive in.