Foil-Roasted Beets and Vidalia Onions With Butter, Lime and Sea Salt. (Renee Comet/For The Washington Post; styling by Bonnie S. Benwick/The Washington Post)

A little salt and sugar, a pair of vegetables whose sweetness is easily coaxed, and butter: That’s all you need to roast the easiest unexpected side dish of summer. The combination works in the oven or in the embers of a grill, because this is packet cooking, pure and simple.

Foil-Roasted Beets and Vidalia Onions With Butter, Lime and Sea Salt

4 to 8 servings

The foil packets can also be roasted directly on the coals in a grill, which can take up to 1½ hours, depending on the strength of the heat.

Serve over couscous or alongside grilled meats.

Adapted from “Turnip Greens & Tortillas: A Mexican Chef Spices Up the Southern Kitchen,” by Eddie Hernandez and Susan Puckett (Rux Martin/Houghton Mifflin Harcourt, 2018).

INGREDIENTS

1 tablespoon sea salt, plus more for garnish

½ cup sugar

4 large beets, trimmed and scrubbed well (a mix of red, golden and/or chioggia beets is nice)

4 Vidalia or other sweet onions

8 tablespoons (1 stick) unsalted butter

¼ cup packed fresh mint leaves (optional)

Lime wedges, for garnish

STEPS

Preheat the oven to 425 degrees.

Mix together the salt and sugar in a small bowl. Cut sixteen 8-inch squares of aluminum foil, then use them to create eight sets of two-ply foil squares.

Place 1 beet on each of 4 squares; same with the onions. Top each with 1 tablespoon of the butter and 1 tablespoon of the salt-sugar mixture. Top with a few mint leaves, if desired.

Wrap each into a tightly sealed packet, placing them all on a rimmed baking sheet. Roast (middle rack) for about 1 hour, until tender with some caramelized edges.

Carefully open each packet, avoiding a rush of steam. Transfer the vegetables to a cutting board; cut the beets into halves or quarters and the onions into bite-size pieces. (If you would like more edges to be caramelized or look a bit charred, place the vegetables directly on the baking sheet and roast (425 degrees) for another 10 to 15 minutes.)

Serve warm, with pan juices, a squeeze of juice from the lime wedges and a sprinkle of sea salt.

NUTRITIONAL ANALYSIS | Per serving (based on 8) 210 calories, 2 g protein, 26 g carbohydrates, 12 g fat, 7 g saturated fat, 30 mg cholesterol, 870 mg sodium, 3 g dietary fiber, 21 g sugar

Tested by Bonnie S. Benwick; email questions to food@washpost.com

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