Sort and soak the black-eyed peas. Pick through the black-eyed peas to remove any pebbles or shriveled peas, then rinse well under cold water. Transfer to a bowl, cover with plenty of fresh water, and soak overnight.

Sauté the aromatics. Set a large Dutch oven over medium-heat. Add olive oil. When the oil shimmers, add the chopped onion and fennel and cook, stirring occasionally, until softened and fragrant, 8 to 10 minutes. Add the garlic and cook for 1 minute more.

Add the black-eyed peas and tomatoes. Drain the soaked black-eyed peas through a colander and add them to the pot with the aromatics. Pour in the crushed tomatoes, and add the salt and pepper. Stir well.

Simmer the peas. Add 2 cups of water, bring to a boil, then reduce the heat to a gentle simmer. Cover partially and cook, stirring occasionally, until the black-eyed peas are tender and the liquid has thickened, 45 to 60 minutes.

Add the spinach. Once the black-eyed peas are soft, add the spinach to the pot, it will wilt quickly. Stir it into the stew and continue cooking until the spinach is tender and well incorporated, an additional 5 to 10 minutes.

Finish and serve. Remove the pot from the heat. Stir in the chopped fennel fronds and lemon juice. Taste and adjust the seasoning with more salt, pepper, or lemon as needed. Spoon into bowls and finish with a drizzle of good olive oil.