What to do with 5lbs heirloom tomatoes?

I agree with the slow roaster suggestions...halve and seed the tomatoes, brush them with some olive oil and sprinkle with a very scant smattering of salt and oregano. Roast at 200-250 for a LONG time (2, 3, 4 hours?) Your nose will begin to tell you when they are done. They will collapse, and become the most lovely, sweet, fragrant things you can eat. Serve them on rounds of toasted bread, either by themselves or with some salty cheese. Store the rest with the juice and some extra olive oil in a jar in the fridge. Try not to eat them all in one sitting (:

I agree with boulangere - I recently turned 5 lbs of tomatoes into tomato sauce, which I canned. Each pound made about 1 half-pint of sauce. Delicious - but not much.

5 pounds of tomatoes isn't really all that many tomatoes. Think small and soon rather than long and many.

Can those babies!

My grandmother wowed me with this crostini topping: quarter the tomatoes and place them along with peeled garlic cloves on a bed of quartered and thinly sliced sweet onions and drown it in the best olive oil you can bear to use. Bake at 275-300 until the tomatoes have completely shrunk but the onions still have a bit of crispness. Let cool. Add to crostini (which you could possibly bake at the same time, right, since it takes about an hour of low heat) and I promise you'll close your eyes. I'd recommend this dish above some of the other suggestions because what you're doing is capturing the amazing tastiness of the tomatoes in the oil, which you can re-purpose now that it's infused with the tomato, onion, and garlic. Tomato sauce would be great with heirloom tomatoes, but tomato sauce tastes really good with less special tomatoes as well, so I think this is a far better use in terms of flavor, texture, and bang for your buck. My grandma remarked that she did not season the mixture at any point, and damn if it wasn't absolutely perfect.

I wacky parsed that as "5 lb tomatoes" and for a bit I was thinking WTH? A 5 lb tomato?

make your own tomato sauce! do something simple like garlic, onion, 1 cinnamon stick and some coriander. It sounds a bit weird but is phenomenal and will allow your delicious tomatoes to shine!

Tomato and mayonnaise sandwiches. Every day.

I'm with sLx and Francesca: make a batch of Marcella Hazan's incredible, unbelievable, amazing, exquisite, brilliantly simple (am I making myself clear here?) sauce with some, and follow Francesca's suggestion with the rest. Oh, and pour yourself a glass of wine.

you can slow roast them to make your own version of sun-dried tomatoes! I've been dying to try this but it doesn't seem worth the effort unless you've got pounds of tomatoes on hand. plus they shrink down so they'll take up less storage space!
tips on how to do it here:
http://www.foodinjars.com/2010/09/slow-oven-roasted-roma-tomatoes/

Gazpacho!

Lucky you! Make this delicious tomato jam. Great for fish, meats, sandwiches or omelettes. As the recipe explains, you can go the short-cut route and eat in the next few weeks or the longer route (sterilized jars) and have summer's goodness to eat in the winter.
http://www.food52.com/recipes/411_sweet_savory_tomato_jam

Put them up and enjoy fresh tomato flavor in January.

Make your own tomato juice and can it. Then you can hoard it away for the best ever Bloody Marys. I've been meaning to post this recipe for a while. If you're interested, I can post it tonight.

Panzanella -- Bread and tomato salad -- is so delicious when you have great heirloom tomatoes. I like to mix it up with peppery wild arugula.

plate. olive oil. salt. fork. knife. go! ok, maybe a hunk of pane pugliese as well ...

What a delicious dilemma! I would suggest making http://www.food52.com/recipes/13722_marcella_hazans_tomato_sauce_with_onion_and_butter and freezing it for future use.

Here's another winning recipe from food52: http://www.food52.com/recipes/5941_heirloom_tomato_and_lemon_mascarpone_tart?fp2r