In a small dish, combine jalapeño, lemon zest and lemon juice; set aside.
Heat half the oil in a large sauté pan.
Add the onion and cook, on medium-high, until it starts to caramelize; remove the onion from the pan; set aside.
Add the mushrooms, to the pan, and cook until they start to brown.
Return the onions to the pan; add the tomatoes and cook until they start to dry out.
Remove from stove, place in a food processor and pulse until very finely chopped.
Add the jalapeño mixture and season to taste with salt and cayenne.
The mixture should have a touch of heat.
Bring a pot of salted water to a boil for the pasta.
Using the sauté pan, over low heat, heat the remaining oil.
Add the garlic; cook until it softens; add the wine.
Increase heat to medium high and cook until the wine has been reduced.
Add the stock and the tomato mixture; stir and add the crab.
When water is boiling, add the pasta and cook until it is al dente; about 3 minutes; drain and add to the sauté pan; add the butter; stir until incorporated into the mixture.
Use tongs to toss all the ingredients together.
Divide among 4 warm plates; scatter tarragon on each and serve.
