Put the avocado in a small bowl and puree it with a hand blender with the zest of half a lime, the juice of half a lime and ½ tsp salt. Beat until smooth. If you don't have a blender, use a wire or a fork. Add in it two-thirds of both fresh herbs (dill, chives). Stir and then refrigerate for 10 minutes.
To make the sauce, mix the tomatoes, capers, remaining lime zest, remaining juice and oil very well and grind the pepper. Set aside until serving.
Grill or toast the bread and then rub garlic on each side of the bread. Let the bread cool, then spread the creamy avocado on each slice and top with the tomato sauce. Sprinkle on top with the fresh herbs. Finish by adding freshly ground pepper and a little oil, and serve.