Tomato is a very strange fruit, or vegetable. Which one is it again? 
It's actually a fruit. A fruit that of course is edible and red, called the "Solanum lycopersicum".
What a confusing genus species name. Do you happen to know when it was first domesticated/harvested?
Well, the Spanish found it when they interacted with the Aztecs, when the Spanish colonies of America. This led them to bring it to Europe in the 16th century!
Interesting, are tomatoes grown off of a plant or do they grow underground?
They grow off the plant, as a berry style. They are really thought of as a culinary vegetable, the perfect ingredient for savory meals and sides!
I love tomatoes for the most part, but I cannot stand ketchup!!! (I call it tomato blood)
of the Aztec Empire, and after the Spanish encountered the tomato for the first time after their contact with the Aztecs, they brought the plant to Europe. From there, the tomato was introduced to other parts of the European-colonized world during the 16th century.
Tomatoes are a significant source of umami flavor.
The tomato is consumed in diverse ways, raw or cooked, in many dishes, sauces, salads, and drinks. While tomatoes are fruits — botanically classified as berries — they are commonly used as
Solanum caripense
Solanum caripense is a species of evergreen shrub native to South America and grown for its edible fruit.
Rare in cultivation, it is known as tzimbalo. The fruit closely resembles the related pepino ("Solanum muricatum"), and it has been speculated that Solanum caripense may be the wild ancestor of the pepino. Like the pepino, the tzimbalo is a relative of other nightshades cultivated for their edible fruit, including the tomato ("S. lycopersicum"), the naranjilla ("S. quitoense")