Wash and dry all produce. Bring a large pot of salted water to a boil. Preheat oven to 200 degrees. Zest 1 tsp zest from lemon, then halve. Squeeze 2 TBSP juice into a small bowl. Halve shallot. Peel and finely chop one half; save the other half for another use. Thinly slice garlic. Chop parsley. Cut tomato into small cubes.

Heat a drizzle of olive oil in a large, preferably nonstick pan over medium heat. Add panko and a pinch of salt. Toast, stirring often, until golden brown, about 5 minutes. Remove from pan and set aside on a plate to cool.

Heat a large drizzle of olive oil in same pan over medium heat. Add crab cakes and cook until browned on bottom, about 4 minutes. Flip and cook until browned on other side, about 4 minutes more. Transfer crab cakes to a baking sheet and place in oven to keep warm.

Once water boils, add tagliatelle to pot. Cook until just tender, about 2 minutes. Scoop out and reserve 1/2 cup pasta cooking water, then drain. Immediately pour reserved cooking water into bowl with reserved 2 TBSP lemon juice, then add 1 tsp flour (we sent more), 1 tsp lemon zest, and stock concentrate. Whisk with a fork until smooth. Stir in capers and their juice.

Melt 1 TBSP butter in pan used for crab cakes over medium-high heat. Stir in garlic, chopped shallot, and a pinch of chili flakes (if you like heat). Cook until fragrant, 30 seconds to 1 minute. Pour in pasta water mixture, bring to a boil, and cook until thickened, about 1 minute. Remove pan from heat and stir in another 1 TBSP butter. Gently stir in tagliatelle and half the parsley. Season with salt and pepper.

Place panko, tomato, and remaining parsley in another small bowl. Season with salt and pepper. Toss to combine. Divide pasta between plates or bowls and top with crab cakes. Scatter tomato mixture over top. Sprinkle with a drizzle of olive oil and chili flakes to taste.