what is it??

When we built the raised vegetable beds back in May and had the soil delievered along with the organic growing mulch, we planted the little seedlings that had been growing since early March. In the middle of June, a mystery plant was sprouting up in the middle of the tomatoes, I didn't pull it out as it didn't look like a weed.
Then, it began to flower and bud.

Does anyone have any idea of what this is going to be when it grows up??