Combine one 14-ounce can no-salt-added diced tomatoes, 2 sliced garlic cloves, 2 sprigs thyme, 2 tablespoons olive oil and a pinch of red pepper flakes in a large microwave-safe bowl; add 2 cups cubed peeled butternut squash. Cover with plastic wrap and pierce the plastic; microwave until the squash is tender, about 15 minutes. Add 1 bunch chopped Swiss chard (stems removed) and toss. Cover and microwave 5 more minutes. Top with crumbled pecorino.