Drain oil from Tuna into a skillet.. Add onions, celery & peppers & saute until soft. Add Tuna and toss to mix. Set aside .. Spread bread slices with Mayonnaise & cut into small cubes. In 1 1/2 Qt casserole arrange layers of half of bread cubes, half tuna mix, half cheese.. Repeat using remainder. Combine eggs with milk..Stir in Tomato Sauce gradually & salt.. Mix well..Pour over casserole. pressing to gently immerse all ingredients. Let stand 10 minutes.. Bake 1 hour at 350 'til golden brown & Puffy..