I normally can my tomatoes using the water bath method. I decided to try pressure canning because . . . well, just because.
You will need about 20 lbs of tomatoes make 7 quarts . . . 7 large tomatoes will fill one quart jar . . . and lemon juice - fresh or bottled (about 1/2 cup)
Make sure you sanitize your jars and lids to prevent mold and fungus contamination which will obviously ruin all your hard work. Imagine the disappointment when you go for a jar of tomatoes to make a fresh pot of pasta sauce and it’s all yucky.
The dishwasher is fine for the jars; especially if it has a "sanitize" cycle or submerge the jars in a large pot (the canner itself) of water and bring it to a boil. Put the lids into the small pot of boiling water for at least several minutes.
Fill the canner about 1/2 full of water and start it heating (with the lid loosely on).
Blanch the tomatoes by placing them, a few at a time, in a large pot of boiling water for no more than 1 minute (30 - 45 seconds is usually enough) and then immerse them into a waiting bowl of ice water. This makes the skins slide right off of the tomatoes! Then cut the tomatoes in quarters and remove the tough part around the stem and any bruised or soft parts.
Fill the jars with the cut tomatoes to within ¼-inch of the top with the tomatoes. Using a flat plastic or wood utensil (like a plastic spoon, up side down) free trapped air bubbles by gently sliding it up and down around the inside edge.
Add 2 Tablespoons of lemon juice and enough liquid to fill to 1/2 inch of the top of the jar.
Wipe the lip of the jars with a towel dipped in vinegar to keep any contamination from preventing a good seal.
Put the lids and rings on. Screw them on snugly, not too tight.
Put the jars in the pressure canner. Put the lid on and screw it down . . . there should be about 3 inches of boiling water in bottom of the canner . . . do not put the weight on yet
Let the canner vent steam for 10 minutes. Keep the water boiling.
After venting, put the weight on (or close the valve) and let it heat up and build pressure to the pressure for your type of pressure canner. Mine is 5 pounds. Then process the jars for 15 minutes
Lift the jars out of the water and let them cool without touching or bumping them in a draft-free place (usually takes overnight) You can then remove the rings if you like. Once the jars are cool, you can check that they are sealed verifying that the lid has been sucked down. Just press in the center, gently, with your finger. If it pops up and down (often making a popping sound), it is not sealed. If you put the jar in the refrigerator right away, you can still use it.
Now, just store them in a cool, dark place and use them as needed over the next year!