8 heirloom or vine-ripened tomatoes, (2-1/2 inches/ 6 cm diameter)
1/2 tsp (2 mL) salt
3 tbsp (45 mL) basil pesto
8 thin slices pancetta, (at least 3 inches/8 cm diameter) or thinly sliced prosciutto
8 small eggs, (at room temperature)
4 tsp (18 mL) butter
Grease 8 mini-muffin or shallow muffin cups; place on rimmed baking sheet. Set aside.
Cut off top of each tomato to make 1-1/2-inch (4 cm) wide hole. With spoon, gently scrape out pulp and seeds. Sprinkle insides with salt ; place, cut side down, on paper towel-lined plate. Let stand for 30 minutes.
Place tomatoes, cut side up, in prepared muffin cups to secure (tomatoes do not need to fit inside cups). Using paper towel, lightly blot insides to remove any moisture. (Make-ahead: Cover and refrigerate for up to 12 hours; bring to room temperature to continue.)
Spoon pesto into tomatoes. Line inside of each with slice of pancetta, pressing down and along side to create hole for egg. Crack egg into each tomato cup; dot with butter. Bake in 400°F (200°C) oven until whites are set and yolks are still runny, 18 to 22 minutes.