Tomato juice on motherboard

Best thing here if your up to it is open the system up again and following the IFIXIT guides disconnect your battery (depending on your model) as soon as you can so you slow down the damage. Follow the guides as needed to disassemble as needed.

Tomato Juice is very acidic so you need to neutralize it. Get a bottle of distilled water (do not use Tap!) with cotton swabs wipe down the areas that got hit with the juice, you can try using a small brush to scrub lightly any areas that need a little more effort, just be careful you don't pull anything off! You may need to soak some areas with the distilled water as the juice could seep under some components. Once you have cleaned & neutralize the spilled juice you'll need to get the remaining water off. Using compressed air (Can'ed Air) blow out the water as best as you can making sure you don't push it deeper inside. Then re-wipe the areas with 85% or better Isopropyl alcohol. This will remove any oils and act as a dryer to remove any remaining water. Still you want to wait a good day or two with the sun warming the system to dry out anything that is left.

If you find this is to big a task get your system to someone who can deal with the spillage as soon as possible as the clock is ticking here!