Put the tomato on a corner?
Yea, here's a poor photo showing some tomatoes on corners of the beds. The most prominent is the grape tomato on the left box. Like 3/5 King said, you really need to control them better than this, especially if it intrudes on your walking paths or you just don't want things overflowing on the lawn. But stake them high and well, you get a lot of production.
In the right bed, at the back, are Early Girl and San Marzano. The best combo shown is the Chimayo pepper and the Beef Maestro (photo clipped on the right). The Maestro is a determinant that stayed low and produced a lot.
Tomatoes, peppers and onions can be good companions. Tomatoes can help provide shade, they usually fare better than most battling the sun. I'm sure they get overwhelmed in record TX heat waves, but that is where the tight spacing would be essential. The corners are prime real estate in a little box.
Anyway, this photo should help sq-ft gardeners realize just what they are in for. I might be an advocate as a "2-sq-ft gardener" in most plant companion situations.