Mix all the marinade ingredients until they are well integrated. Wash the cauliflower well and spread the marinade over the entire surface.
Place the stainless steel inner pot inside the Instant Pot®. Press Saute and set time to 10 Minutes. Add the oil and wait about a minute until it is hot. Add the onion and whole garlic for the sauce until well cooked. Add the sauce ingredients: salt, colored chile pepper, lemon juice and oil. Stir well, then press Cancel.
Put the rack in the bottom of the Instant Pot®, 1 cup water and then put the cauliflower on it. Press Cancel, close and lock the Instant Pot® lid. Make sure the steam release handle is turned to Sealing. Press Pressure Cook, pressure level High, and set the time to 3 Minutes. Once the time is up, press Cancel and let the pressure release naturally for 3 minutes. Once all the steam has been released, open the lid.
Very carefully transfer the cauliflower to a baking tray and bake for 3-5 minutes on GRILL to brown it on top (this step is optional)
In the Instant Pot®, press Saute and set the time to 10 Minutes. Let the liquid boil and then add the corn starch. Stir and then press Cancel. Process all the ingredients for the sauce with an immersion blender until a uniform mixture is obtained. Press Saute again and set the time to 5 Minutes. Stir for 3-4 minutes, then press Cancel.
Serve immediately spooning the sauce over the whole cauliflower.