1 Baking sheet, 1 Bowl, 1 Cutting board, 1 Large knife, 1 Small knife, 1 Tablespoon, 1 Mandoline, 1 Sieve, 1 Immersion blender, 1 deep bowl, 1 Salad spinner, 1 Oven rack, 1 Can opener
1 Rinse tomatoes, wipe dry and cut out stems. Cut tomatoes into quarters and scrape out seeds.
2 Peel the garlic and finely chop. Rinse thyme and rosemary, shake dry, pluck leaves and finely chopped. Mix together garlic, thyme, rosemary and 1 tablespoon olive oil. Season with salt and pepper. Place the tomatoes, cut side up, on a baking sheet fitted with a wire rack. Drizzle tomatoes with the olive-oil mixture. Bake tomatoes on middle rack of preheated oven at 110°C (fan: 80°C, gas mark 1) (approximately 225°F) until shriveled and dried, 2-3 hours.
3 Remove tomatoes and let cool. (Tomatoes can be prepared a day ahead.)
4 Squeeze juice from lemon. Drain tuna and mix with the yogurt, sour cream, drained capers, olive oil and 1 tablespoon lemon juice. Season with salt and pepper.
5 Rinse celery, pat dry, remove any strings and thinly slice.
6 Rinse lettuces, spin dry and cut or tear into bite-sized pieces. Spread tomatoes on a plate, spoon tuna sauce over tomatoes and top with lettuces and celery. Serve immediately.