1/2 cup basil pesto, for topping (optional but recommended)
2 tbsp fresh basil leaves, chopped
Place the eggplant and zucchini slices on a large cutting board and sprinkle with salt. Allow to sit for 20-30 minutes so they release some water. Wipe the water and salt away with a paper towel.
In a small bowl, mix together the ricotta cheese, egg and parmesan until smooth.
Grease a round 7-inch baking pan. Place a thin layer of sauce onto the bottom of the pan. Top with one layer each of zucchini, eggplant, ricotta mixture then the shredded cheese. Continue layering once more, ending with a final layer of just sauce and cheese (I like to make my top layer of cheese the thickest).
Pour 1 1/2 cups of water into the bottom of the Instant Pot, then place the trivet inside. Make a foil sling out of tinfoil (a long piece of tinfoil folded twice lengthwise) and place baking pan on top. Cover baking pan with additional foil (spray it with a little cooking spray so cheese doesn't stick), then, using the sling, carefully set the pan onto the trivet, folding down any tinfoil so that it doesn’t interfere with closing the lid.
Close the lid, press “Manual” and immediately adjust the timer to 20 minutes. Check that the cooking pressure is on “high” and that the release valve is set to “Sealing”.
When time is up, allow the IP to naturally release pressure for 10 minutes, then open the IP using “Quick Pressure Release”. Using the foil sling as “handles”, carefully remove lasagna from IP. Remove foil, and pop under the broiler a few minutes to brown cheese. Allow to rest for 10 minutes, then serve. Top with basil pesto and freshly chopped basil, if desired.