Whole grain bread (rolls work best)
Aged yellow cheddar (low-fat)
Not-too-ripe Roma tomato
Red onion
Fresh baby spinach
Garlic powder
Cracked black pepper
Drizzle of extra-virgin olive oil (a good fat)
Pinch of sea salt or kosher salt (optional for those on low-sodium diets)
Sliced fresh mozzarella

Layer accordingly (top with other piece, of course!)
Place on non-stick sprayed pan. Weigh down panini-style with heavy skillet, roughly 3-5 mins each side on medium-high heat.