Lime is a soil amendment used for root & flower/fruit development. It's rich in potassium & phosphorus. Add it to the planting hole (especially for tomatoes) or as supplemental feeding.

But only on plants which like a slightly alkaline soil, such as most commonly grown vegetable.

This link goes in to the nitty gritty of when, which and how much lime to use. https://www.rhs.org.uk/advice/profile?PID=144