Besides using it for sandwiches, I also use it for stuffing or dressing, french toast or toast. (mynaturalfamily.com)
I used up leftover tomato paste and a tiny chunk of red onion that we were using for our sandwiches during the week. (staceyhomemaker.com)
Side note: I've been obsessed with roasted garlic lately, and have even been known to eat it plain... So I wanted to use it for this sandwich too. (thrive-style.com)