Preheat a grill to medium low. Brush the focaccia with 2 tablespoons olive oil. Grill the bread until lightly toasted, 2 to 3 minutes per side. Cut into cubes and transfer to a large bowl.
Add the tomatoes, escarole, cucumbers, basil, capers, red wine vinegar and the remaining 3 tablespoons olive oil to the bowl; season with salt and pepper. Top each serving of salad with tuna.
Photograph by Antonis Achilleos
Courtesy of Food Network Magazine