Begin with the chicken. Preheat grill to 350-400 degrees. Season chicken with lemon juice, garlic powder, oregano, paprika, salt & pepper, and if desired, cayenne. Grill 8 minutes per side or until cooked through.
While the chicken is grilling, split or slice the loaf of bread and toast it (on the grill or under oven broiler). Just lightly toast, and while it is still warm, rub with a clove of garlic.
While the bread is toasting (but don't forget about it!), slice the tomatoes in half and grate them with a box grater directly into a bowl until you reach the skins. Discard the skins. To the tomato pulp, add a drizzle of olive oil and salt to taste.
To serve, spoon the tomato pulp mixture onto the bread, and serve alongside the grilled chicken. Recommened sides: Spanish cheeses and olives, and/or a side salad.