1. Preheat broiler with oven rack 5 to 6 inches from heat. Brush both sides of bread with butter; place on an aluminum foil-lined broiler pan. Broil 1 to 2 minutes on each side or until lightly toasted.
2. Prepare hollandaise sauce according to package directions; stir in zest and 1/2 tsp. lemon juice. Keep warm.
3. Toss together arugula, next 2 ingredients, 2 tsp. olive oil, and remaining 1 tsp. lemon juice.
4. Heat remaining 1 tsp. olive oil in a large nonstick skillet over medium heat. Gently break eggs into hot skillet; sprinkle with salt and pepper. Cook 2 to 3 minutes on each side or to desired degree of doneness.
5. Top bread slices with arugula mixture, pancetta slices, and fried eggs. Spoon hollandaise sauce over each egg, and sprinkle with tomatoes. Serve immediately.