In medium saucepan on medium low heat, place butter in sauce pan and melt. To melted butter stir in flour and salt; Stir briskly, until flour and butter turns into a thick paste; do not brown. Add to mixture slowly half and half and stir briskly until it thickens slightly. Add Parmesan cheese, Monterey Jack cheese, 1/4 Cup Mozzarella cheese and artichokes. Stir cheese mixture until heated through. Add 1/4 cup reserved artichoke juice and lemon juice, stir. Add fresh chopped spinach and bacon bits, stir well. Heat until all is blended and mixture starts to bubble very lightly, remove from heat. Place in oiled shallow casserole dish; sprinkle remainder of mozzarella cheese on top. Place in a preheated oven at 350 degrees F for 15 - 20 minutes. Remove and sprinkle with diced tomato for garnish. Serve with Focaccia or crusty garlic bread.