To make the sauce, heat the extra virgin olive oil in a large skillet or medium saucepan over medium heat. Add the onions and cook, stirring, until starting to color, about 4 minutes. Add the garlic and cook, stirring, for 30 seconds. Add the anchovies, lower the heat, and stir, crushing them into a paste against the sides of the pan. Add the tomatoes, capers, red pepper flakes, and white wine and simmer until the sauce thickens, about 15 minutes. Add the parsley, butter, and lemon juice, and stir to combine. Remove from the heat and adjust the seasonings to taste. Cover to keep warm until ready to serve.
Combine the flour and Essence in a shallow dish. Dredge the roe in the flour, shaking to remove any excess.
In a large skillet or saute pan, heat the oil over medium-high heat. Add the roe and cook until lightly browned, about 3 minutes per side. (The roe still will be slightly pink inside.) Remove and lightly season with salt and pepper.
Divide the roe among 4 plates and serve with the tomato-anchovy sauce on the side.
Yield: 4 servings