Soak the kale in a tub of water for at least 10 minutes to allow any dirt to come off. (If you want to cut down on bitterness, do this after preparing your leaves as shown here.)
Then (one leaf at a time) lay a leaf on your cutting board.
Fold it in half.
Cut along the hard rib all the way down.
The leaf should now be completely removed from the stem.
Chop or tear the leaves into bite-sized pieces. (If you haven't soaked your leaves yet, do so now.
Place the leaves in a salad spinner and spin to dry.
Place the leaves in a large mixing bowl.
Add your minced shallots.
Add the lemon juice.
Sprinkle on just a small pinch of salt (optional, but tasty)
Add in the avocado and squish/knead everything together for about 3-5 minutes.
When finished, your hands should be dirty and your kale should be nice and soft/pliable. Taste and season with salt and pepper as desired.
If using the tomatoes (I didn't, but I have in the past and it's super good), toss them in now, and then serve.
Notes
Please note that the nutrition data given here is a ballpark figure. Exact data is not possible. Data does not include the optional tomatoes.