Roasted Onions And Green Beans

⏲ ~24 min total · prep 15 · cook 9 · 4 servings

By the KFI Test Kitchen · Tested & approved by Jason Lieu, KFI recipe editor

Published Sep 15, 2026 · Updated Sep 15, 2026

Ingredients

• 12 oz green beans, trimmed
• 1 medium yellow onion (about 6 oz), cut into 1/2-inch wedges
• 2 tbsp olive oil
• 1/2 tsp kosher salt
• 1/4 tsp black pepper
• 2 cloves garlic, smashed
• 1 tsp fresh lemon juice
• 1 tbsp toasted slivered almonds

Instructions

1. Heat the oven to 425°F with a rimmed half-sheet pan on the upper rack — a screaming-hot pan sears the vegetables on contact instead of steaming them.
2. Toss the beans and onion wedges with the olive oil, salt, and pepper in a large bowl until every surface glistens.
3. Pull the hot pan out, spread the vegetables in a single layer, and set the onion wedges cut-side down; it should sizzle on contact.
4. Roast 12 minutes without touching them, until the bean undersides blister and the onion cut faces go deep gold.
5. Flip and stir the vegetables, scatter the smashed garlic over, and roast 8-10 minutes more, until the bean tips blacken in spots and the onions turn jammy at the edges.
6. Hit the pan with the lemon juice, toss, and pile onto a platter with the toasted almonds. Serves 4.

Why this recipe works

• A screaming-hot pan The half-sheet preheats to 425°F on the upper rack, so the vegetables sear on contact. Cold pans give you gray, limp beans.
• Onions cut-side down Set with their cut faces against the metal, the wedges go deep gold and jammy at the edges by the time the beans blister.
• Garlic in late Smashed cloves join for the final 8 to 10 minutes, long enough to turn gold, short enough to skip the burn.

Tips for making this recipe well

Single layer, no crowding

Vegetables stacked two deep steam each other. Pull out a second pan if the first looks full.

Hands off for 12 minutes

The blistered undersides form only where the bean touches hot metal. Stirring early resets the clock.

Listen for the sizzle

Vegetables hitting a properly preheated pan should sizzle on contact. Silence means the pan was not ready.

Lemon off the heat

The tablespoon of juice goes on after the pan leaves the oven, tossed right on the hot metal. It lifts the jammy onion edges.

Almonds at the platter stage

Toasted slivered almonds go on after the toss. Mixed in earlier, they soften against the hot vegetables.

Serving suggestions

Serves 4 as written, and we put it beside eggs more often than beside anything else; the pan comes out of the oven while the omelet rests. At 3.7 g net carbs the whole pan fits a keto day with room to spare. Pile the vegetables on a platter, pour the pan juices and lemon over, and scatter the almonds last. The onions are the part people reach for first, jammy and gold at the edges.

Storage and meal prep

The beans keep 3 to 4 days in an airtight container in the refrigerator. They soften as they sit, blistered turning tender, and the flavor holds; reheat spread on a pan in the same 425°F oven for a few minutes. They freeze for 2 to 3 months, but thawed green beans land soft, so we freeze a batch only when it is headed for scrambled eggs, where texture matters less.

Variations worth trying

• Red pepper flakes Toss 1/4 tsp in with the oil, salt, and pepper. The heat bakes into the blistered spots.
• Shallots instead of onion Swap in 2 or 3 halved shallots at the same cut-side-down treatment. They turn jammy faster, so start checking at 8 minutes.
• Parmesan finish Grate a little Parmesan over the platter right after the lemon. It clings to the hot beans and softens into a rind.

Frequently asked questions

Do I need to blanch the beans first?

No. Twelve minutes on a 425°F pan cooks them through while the undersides blister. Blanching first adds a wet surface, which is how you steam them.

Why preheat the pan?

A screaming-hot pan sears the vegetables on contact. Cold pans let them release moisture first, and you end up steaming them gray.

Can I use frozen green beans?

Not for this recipe. Frozen beans release water as they thaw and never blister; the recipe is built on fresh, trimmed beans.

How big should the onion wedges be?

Half-inch wedges, per the recipe. Cut much smaller and they burn before the beans have time to blister.

Can I add other vegetables?

Keep them quick-cooking and low-moisture. Broccoli florets roast on roughly the same schedule; watery vegetables such as zucchini turn the pan soupy.

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