Obviously misunderstood.
But to address the question of how to toast a tomato:
You make the sandwich first, open faced, two pieces of bread side by side on a plate, (to be clear and specific for these guys

) with the tomater slices and whatever else on it.
Then you nuke it for 20-30 seconds or so til the tomatoes and other innards you put on it are at or above room temperature.
Add the cheese.
Then stick it in a preheated rack type air fryer at 400°F (204°C) and watch it. When the cheese starts melting, it's done. Like 2-3 minutes. (Any longer than that & the bread turns into salad croutons.)
Assemble the sammich.
Next, what you do now is you eat it.
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Edit: I don't think I actually answered the question..
OK, here's how you toast a tomato.
Put the tomato slices out on parchment paper like you're making cookies.
Stick 'em in the air fryer at it's highest temperature, keep the light on and observe through the door and keep checking on it til you are confident that you have successfully toasted tomatoes.
Then report back to this thread, cuz I really don't know how it would turn out.