Core the tomatoes and cut into wedges. Remove the top of the fennel (save some fronds for garnish) and slice the bulb very thinly crosswise with a knife or on a mandoline.
Toss the tomatoes and fennel in a bowl with the olive oil, lemon juice, vinegar, salt, and pepper. Garnish with 2 tablespoons chopped fennel fronds, season to taste, and serve.
2005, Ina Garten, All Rights Reserved