Rinse greens in a bowl of cold water, swishing to loosen dirt, then lift into a colander — don't pour. Repeat if sandy. No need to dry fully; clinging water helps them cook. Remove thick inner stems and discard. Coarsely chop leaves into manageable pieces with no long strands. If stems are tender (like chard), slice into strips and set aside to cook first. Mince garlic and prep aromatics before you start — the pan moves fast once it's hot.

Heat a large skillet over medium to medium-high heat with 2 tbsp olive oil until shimmering. If using stems, onion, or garlic, add those first and sauté about 1 minute until softened and pale golden — watch the garlic so it doesn't burn. Add greens in large handfuls, letting each wilt slightly before adding the next. Toss to coat with oil. Once all greens are in, sauté occasionally, seasoning with a pinch of salt. Cook 3–8 minutes total: spinach ~3 min, heartier greens (kale, collards, chard, beet greens) ~5–8 min. Splash in a little broth or water if the pan looks dry. Done when leaves are tender and still bright green. Stir in any spices like red pepper flakes or cumin in the last minute.

Once greens are tender and still bright green, pull the pan off the heat. Add a squeeze of lemon juice or small splash of vinegar to brighten flavor and cut bitterness. Season with salt and black pepper. Serve immediately — they lose texture and color fast. Key doneness cue: dull, olive, or mushy means overcooked. Pull them the moment they're just tender.