Scientists Discover the Genes for Supersizing Fruit

When Spanish explorers first brought domesticated tomatoes to Europe 500 years ago, the fruit was already gigantic compared with its olive-sized wild counterparts. Researchers trying to understand the genetic basis of this girth have uncovered a way to make other fruits larger as well. The team discovered this secret by studying two mutant tomato strains that had many branches coming off the upper part of the stem and that produced unusually fecund fruit.

Source: Scientists find way to create supersized fruit

Tomatoes are technically a fruit.  More specifically, they are berries, and the wild tomato was indeed berry-sized.