1
Cut bread in half lengthwise. Scoop out crumbs from both halves, leaving 1/2-inch-thick shells.
2
Process the crumbs in a food processor or blender until finely chopped; set aside.
3
Whisk together lemon juice, oil and garlic in a large bowl. Stir in the reserved breadcrumbs, tuna, tomatoes, bell peppers, scallions, olives, capers and thyme; mix well. Season with salt and pepper.
4
Spoon the breadcrumb mixture into the bottom bread shell and replace the top. Cut crosswise to serve.
