Pre-heat oven to 300 degrees. Toss bread cubes in a bowl with olive oil, salt, garlic powder and cayenne then spread in an even layer on baking sheet. Bake until golden brown and crunchy, about 20 minutes.
Whisk together dressing in a bowl; set aside.
When you're ready to assemble, place romaine hearts on a platter and drizzle with dressing and top with croutons.