NYT Cooking: This makes a substantial vegetarian – or vegan if you leave out the cheese – Thanksgiving main dish. It is another riff on the native American tradition of the Three Sisters – corn, beans, and squash. I used acorn squash here, and it serves as a vessel for the sweet and pungent bean, corn and tomato filling. Acorn squash comes in various sizes; the larger ones, which are sometimes all I can fin...