Keeping scrambled eggs with tomatoes from being too watery
Another effective method (not mentioned in the link SAJ14SAJ provided) is salting. Dice the tomatoes, generously salt them and leave them in a sieve for 20 minutes or so. You probably want to squeeze off some of the juicy bits first. Flip the tomatoes half-way through the resting time. That will draw off a lot of water without pre-cooking the tomatoes (which will also work, but will change (not necessarily negatively) the taste of the tomatoes. If you use kosher or other coarse salt, you'll be able to shake or wipe off quite a bit of the salt before proceeding with your application.