Cut the veggies into cubes and set aside.
Turn on your instant pot and select saute (more settings), add olive oil and leave until hot.
Add chopped onions and saute until soft (this should take about 3 minutes) add chopped garlic and continue to stir for another minute.
Next, add in the chopped zucchini, eggplant and red bell pepper and continue to saute for another 2 minutes. Followed by the tomato puree, basil, thyme, salt and the chopped tomatoes. Mix to combine for another minute.
Finally, pour the vegetable stock over it, stir to combine making sure nothing sticks to the bottom of the pan and if there is, make sure to scrape it off to avoid getting a BURN notice.
Secure the lid of the instant pot and turn the valve to the seal position. Select the manual or pressure cook button then cook on high pressure for 3 minutes.
Once the cycle is completed, carefully do a quick release. Stir to combine, if there is too much liquid in the ratatouille, turn on the saute function and stir until the liquid reduces in size.
Serve as desired and enjoy.