Hmm. So does this electric oven not have a stove top burner? In my opinion, liver should be cooked like a steak: over high-ish heat and breifly so that the interior stays quite pink (medium-rare to medium at most). If you overcook liver, it gets dry and get a really terrible crumbly/chalky texture.
If you don't have a stove top burner, I guess I would recommend using the broiler in the oven and putting the liver on a baking sheet pretty close to the broiler so you can sear it. Whatever you do, don't overcook it. I would not use the microwave. I think I would sooner eat it raw.