Dice up the leek, celery, carrot, and bell pepper (I'm going to call this the mirepoix, even though it technically isn't)

Peel the shrimp, reserving the heads, tails, and shells for the sauce.

In a large saucepan, heat 1 tbs of oil over medium heat and sauté the mirepoix (with the bay leaf) until tender.

Add in the tomato paste and and stir until combined.

Add the reserved heads, tails, and peels to the mirepoix, mix to coat with oil, and press down on them a few times with a spatula to get out all that good shrimp flavor. Sauté for another five minutes or so until the shrimp parts turn red, stirring and pressing occasionally.

Add the chicken stock, bring the heat up to a boil, then reduce and let simmer until stock is reduced by 1/2 or so.

In the meantime, make a brown roux with the butter and flour. I did this by melting the butter, adding in the flour and stirring continuously over medium heat for about six minutes or so until it turned caramel colored and gave off a nutty smell. Set roux aside.

When sauce is reduced, pour the contents of the sauce pan into a strainer over a small saucepan until all you have is the liquid broth.

Add the celery seeds, paprika, and black pepper to the broth. Bring up the heat and incorporate the roux. Reduce until sauce coats the back of a spoon -- runny but not watery. NOTE: I would use between 1 and 1 1/2 tbs of the roux -- I put 2 tbs in the recipe to err on the side of caution. Taste the sauce and season as necessary; I didn't add any salt because the chicken stock had enough already.

In a separate pan, heat 1 tbs oil over medium and cook the shrimp with the lemon juice, the dried parsley, and the pepper. I cook the shrimp in batches to avoid crowding. Season to taste.

For the tomatoes, cook them over medium heat with 1/2 tbs of oil until tender or you can cook them in batches with the shrimp. Season to taste.

Add shrimp to plate, pour on the sauce, top with tomatoes and capers, and serve.