Combine oil, onion and garlic in a heavy medium-size saucepan over medium-low heat. Cook, stirring, until mixture is fragrant and golden, about 4 to 5 minutes. Add beans and sage; cook, stirring, until hot, about 5 to 6 minutes.
Stir in tuna and cook until just heated through, about 2 minutes. Season to taste with freshly ground white pepper. Garnish with chopped tomatoes and parsley, if desired. Serve immediately.
My husband and I are not picky eaters. In an effort to save money, we do not waste food. This went in the garbage. Even with extra seasoning (Italian seasoning mix, salt and pepper) and the addition of cheese, it was dry and flavorless.
Very bland. I added diced tomatoes w/green chilies, but it was still rather boring. A sprinkle of cayenne pepper help a bit. I'll try it as a cold salad with romaine lettuce tomorrow. Maybe it will taste better cold.