How do I get rid of that calcium chloride taste in my tomato sauce?
To begin with, you can microwave the tomato before cooking it in the pan; this will also shorten the cooking time. Doing this, the tomato "grains" will already be hot inside when they begin to cook from the outside in the pan. You'll still get the external "roasted" feel but with a softer texture. 

You can compensate for the citric acid, and for the excess of the tomatoes' own acid, by adding some sugar.

In order to hide the metallic taste, add some herbs. Try one leaf of bay laurel; or a combination of dry herbs like savory, fennel, basil, thyme, and oregano.