Clean the smelts and remove the head, tail, fins and bones, steaming them very briefly (1 minute) and carefully detach the fillet. Cut the cleaned fennel bulb into slices and finely chop the greens. Steam the fennel slices for 5 minutes, then drain them well in a sieve and cool. Peel the fresh tomatoes, remove the stem and the inside with the seeds (also for canned tomatoes) and cut the tomato flesh into cubes.
Preheat the oven to 150 degrees, grease a gratin dish with the olive oil and layer a third of the pint filets in it, season with salt and pepper and drizzle with juice of one lemon.
Then form half of the fennel slices and on top all the tomato cubes. Season again with salt and pepper and layer the next third of fillets on top. This you treat as the first layer, form following fennel slices and the last layer of poutine fillets on top. On top of it form the rest of the juice of one lemon, the fennel greens and again salt and pepper.
Now cook the casserole covered at 150 °C in the oven for about 15 min.