Healthy Baked Tomatoes with Cheesy Oat Crumble

Basil, large fresh leaves

Lemon, large

Scallions, thinly sliced (about 3 tablespoons)

Tomatoes, medium vine-ripe

Oats, old-fashioned

Kosher salt and freshly ground black pepper

Whole wheat pastry flour

Olive oil, extra-virgin

Butter, unsalted

Parmesan