Step 1

Preheat oven to 425°F. Line a rimmed baking sheet with parchment paper.

Step 2

Place squash in a large microwave-safe bowl and add water. Cover with plastic wrap and microwave on High until just tender, 8 to 9 minutes.

Step 3

Meanwhile, mash garlic and salt together with a fork or a chef's knife on a cutting board, then transfer to a small bowl. Stir in oil, jalapeño and ground pepper.

Step 4

Lay one squash half, cut-side down, between 2 wooden spoons and make cuts 1/4 inch apart, cutting down just to the spoons so the squash remains intact. Carefully transfer to the prepared pan. Repeat with the other half. Brush the oil mixture over the squash, pressing it between each cut.

Step 5

Roast until the squash is lightly browned, 30 to 35 minutes. Serve garnished with cilantro, if desired.