Dice onion into small pieces (or skip this step and use a 10-oz package of frozen diced onion)
Use ½ tsp avocado or coconut oil to grease bottom of Instant Pot.
Set Instant Pot to "saute" setting, and dump in the onions. Let the onion saute while you prepare the rest of the veggies. You may need to stir occasionally to keep it from burning.
Wash celery and carrots. Peel the carrots. Dice the carrots and celery.* (Or see note below and just blend them in the blender.)
Open the cans of diced tomatoes and add them to the sauteing onions in the Instant Pot.
Add the diced carrots and celery to the Instant Pot.
Use a garlic press to crush the garlic and add it to the Instant Pot.*
Add the 6 cups of filtered water to the Instant Pot.
Dump in the frozen chopped spinach.
Open the can of pumpkin and dump that in, also.
Rinse the lentils and dump them into the Instant Pot.
Stir everything. Then, seal Instant Pot and set to 40 minutes on high pressure.
After it has finished cooking, allow to de-pressurize naturally for 20 minutes. Then vent manually.
Add about 1 TB Spike spice mix and stir. Then serve, or divvy up into jars for later meals.