Roast 3 yellow bell peppers under the broiler or over a flame, turning with tongs, until charred all over. Transfer to a bowl, cover tightly with plastic wrap and let cool.
Meanwhile, in a small skillet, add the shallot, garlic, olive oil and salt and pepper to taste. Cook over medium heat, stirring, until softened, about 5 minutes. Add the cumin and cook for 1 minute more. Let cool.
Peel the roasted peppers, discarding the stems and seeds, and transfer to a food processor; add the cream cheese. Process until nearly smooth, transfer to a bowl and stir in the cooled shallot mixture and the sour cream. Cover and refrigerate for 1 hour or up to 2 days.
In a medium pot of boiling water, cook the green beans for 1 minute. Drain and rinse with cold water. Peel the jicama and cut into 3/4-inch-thick spears; toss with the lime juice. Slice the remaining yellow bell pepper lengthwise into strips.
Season the dip with salt and pepper and serve with the green beans, jicama, red bell pepper and tomatoes.