Besides I LOVE, LOVE, LOVE hearing the pop coming from the jars when the vacuum effect takes place which causes the seal pop down and seals. You know it is coming but you don't know exactly when. It is almost musical and magical :)
Adapted from Eating Local
3 lbs of large slicing tomatoes, about 1/2 lb each
dried italian herb
extra virgin olive oil
Core and slice each tomato in half horizontally. Place on rimmed baking sheet, cut side up. When all the tomatoes have been sliced and placed on baking sheet, you can season them. Sprinkle each tomato generously with salt, dried italian herb and granulated garlic in turn. Finally drizzle each tomato with extra virgin olive oil. Place in oven and roast for 3 hours until they are very soft and just about to caramelize.
Use a bubble remover / headspace tool or a skewer, if you do not have the former, around the edge of jar contents to release air bubbles. Take your time to remove the bubbles or you may not get a good seal on the jars.
Wipe the threads of jar clean with a damp clean cloth. Remove sterilized lids with tongs or magnetic wand. Cover filled jars with sterilized lids. Tighten just to hand tight. Process in hot water bath for about 30 minutes. Use a Jar Lifter to remove jars and cool on counter. You should hear the seal set when a pop is heard. This will take place over the next few hours and up to 24 hours.
After it has cooled for 12 to 24 hours, check the seal by pressing the center of lid. The safety button in the center should not flex. If you remove the ring, you should be able to hold the jar by the seal. If you find that some jars that are not sealed, place jars in the refrigerator and use within a few days.