This the easiest method of canning tomatoes, I know. Start by reading Canning Made Simple, here on this blog.
What you will need:
20 Medium to Large Tomatoes
2 Quart Jars with lids and rings
Take a large microwave safe bowl and pour in water up to 1/2 full. Float, stem side up, as many tomatoes as will fit without crowding. Stick in microwave for 15 to 20 minutes. When tested, you want the skin to wrinkle when touched.
You will need a clean microwave safe bowl and a trash bowl. Over the trash bowl, cut top out of tomato and discard. Over the clean bowl, hold the tomato, top side down and squeeze. The peel should be in your hand, and the tomato in the bowl.
Now, for the fun part. You will either need to use a potato masher or your hands, for this step. All the tomatoes need to be mashed, without any large lumps.
When your tomatoes finish cooking and the dishwasher is about finished with the drying mode, you can start filling your jars. Take one jar out at a time, and using a ladle, fill up to 1/2" from the top. Using a clean paper towel, wipe any residue off rim of jar. Now, take a ring and lid from the dishwasher and seal the jar. Fill the next jar the same way.
Do not push on tops. Allow to seal on its own. Store in cool dry place.