In a large skillet (ideally with high sides) over medium heat, cook onion, fennel, and garlic in olive oil for 8 minutes, season with salt and pepper (about 1/4 tsp of each). Add canned diced tomato, fresh tomato, kale, and water. Stir well and cook for 12 minutes. Add crushed red pepper, fresh oregano, and olives.
Prepare fish, season with salt, pepper, orange zest and fennel seeds (optional). Nestle fish into kale tomato stewing mixture. Cover pan and cook for 10 minutes.
Remove from heat, and finish with fennel fronds, more fresh oregano, more orange zest, and a drizzle of olive oil on top.
This is definitely a complete meal but it is also quite lovely served with a grain on the side, just be sure to pour lots of that yummy sauce over the grain