For the sauce: Place the yogurt, parsley, olive oil, lemon juice, lemon zest, cumin, pepper and salt in a food processor. Process until smooth, scraping down the sides with a rubber spatula as needed, about 30 seconds. Set aside
For the fish: Heat the olive oil in a large skillet over medium-high heat. In a shallow bowl, combine the flour with the coriander and salt. Dredge each fillet in the seasoned flour and coat well. Shake off excess flour, then add the fillets to the hot pan. Cook on the first side for 3 to 4 minutes, or until golden brown and cooked most of the way through. Carefully flip, and cook for another 1 to 2 minutes.
To assemble: Brush the bread slices with the olive oil and toast on a grill or grill pan over high heat for 3 minutes per side, or until golden brown.
Spread each slice with a few tablespoons of the sauce and place a fish fillet on top. Add another dollop of sauce and scatter over some arugula and cherry tomatoes. Add a squeeze of lemon, season with salt and serve.