Blight is a fungus that can live in the soil and on dead plant material.

Ensure to clean up the area very well of all dead plant material and destroy it.

You then need to plant your tomatoes in another spot for the next three years. The best way really is if you have three completely different separate areas that you rotate crops.

So if you have three (or more) raised beds, rotate your plants between all of them; a different bed each year. Do this with most of all your plants if possible because this helps to keep the area from building up bacteria and fungus.

I had fusarium wilt last year on my tomatoes so I moved them this year and didn't have the problem. I plan to rotate the tomatoes to the front yard next year.

Here is a link that might be useful: BsnTech Gardening Blog