How to get best taste out of tomatoes

If you are really set on doing this, just use the same amount by weight or volume, preferably peeling the tomatoes first. (Cut an x in the bottom, dip in boiling water for 10 seconds, pull off the peel). You'll have plenty of liquid coming out of the tomato, don't worry about that. But honestly, I don't recommend doing this. Fresh tomatoes that are any good are so good uncooked that it is a waste, and fresh tomatoes that aren't good won't get better by cooking them. Even Mario Batali says you should use canned tomatoes for cooked sauces.

Tomato paste is just tomatoes with the water removed, essentially. I'd slice the tomatoes in half and roast them (cut side up) at 350 degrees F for an hour (this will concentrate the flavour nicely and you can add s&p/olive oil/herbs/garlic if you want). Then mash them through a sieve or food mill to get a smooth consistency. Then put that tomato puree in a pot and just boil them down until it's as thick as you want. As it gets thicker, you'll need to stir it regularly to prevent it sticking to the bottom of the pot and burning.