What's this plant
Well, one thing for sure, the plant in the pictures you sent is a weed and not a tomato. The weed shown is called Velvetleaf and is common and quite a pest in corn producing areas. I assume you planted your tomato from seed and the Velvetleaf seed was probably already present. They thrive in nutrient-rich soils, thus a garden bed or a nice container on a patio, is perfect. The "fruit" are the large cup shaped disks you see and each contains 9-15 seeds. Just pull the weed and make sure none of the cup-shaped seed pods have opened or fallen onto the soil and dispose of it.
I hope you have a great late summer and remember, a patio container is a great place for a small, fall vegetable or flower garden.