There is no need to "tenderize" calamari when you are high heat sauteeing. Tenderizing calamari in a mixture of milk and salt is a common recommendation for fried calamari. This is not needed in this calamari saute recipe. The calamari will be tender, as long as you don't overcook it. Calamari should be cooked for 2 minutes or one hour - anything in between will produce tough results.