1. Preheat standard oven to 400°F. Place pancetta in single layer on full sheet pan. Bake 12 to 15 minutes or until cooked through, but not crisp. Remove and drain on paper towels.
2. Drizzle olive oil over tomato slices; sprinkle with salt. Let stand 5 minutes.
3. Spread 1 Tbsp. of the Lemon Aioli on one side of each slice of bread. Arrange slices of pancetta evenly over four slices of bread. Top with tomato slices and arugula. Cover with second slice of bread.
4. Spread outside of sandwiches with softened butter. Grill in a heated panini press 3 to 5 minutes or until bread is golden and filling is hot. Cut sandwich in half and serve.
Nutritional information per serving: Calories 724; Total Fat 32g; Saturated Fat 9g;