Any hearty green can be used in place of kale in this recipe. For the best results, make the filling a day in advance -- it tastes even better once the flavors have had time to mingle.
Preheat oven to 350 degrees. Cut off top third of each tomato, and reserve. Leaving a 1/2-inch-thick shell, scoop out insides, and coarsely chop. Place 1/2 cup in a bowl, and discard the rest.
Toast coriander, cumin, and fennel seeds in a small pan over medium heat, swirling pan, until spices are fragrant, about 2 minutes. Transfer spices to a spice grinder, and add red-pepper flakes. Process until finely ground, then stir in cinnamon.
Heat oil in a medium saucepan over medium heat. Add onion, garlic, 2 teaspoons salt, and the serrano chile. Cook, stirring occasionally, until onion is translucent, about 5 minutes. Stir in chopped tomatoes, and cook until most of the liquid has evaporated, about 3 minutes. Stir in spice mixture, and cook for 30 seconds.
Add rice to pan, and stir to coat. Stir in 1 3/4 cups water. Bring to a boil, then reduce heat to a simmer. Cover, and cook until rice is al dente, about 14 minutes. Add kale, and cook, stirring, until just wilted, about 2 minutes.
Place currants and orange juice in a small bowl, and let stand for 15 minutes. Stir currants, juice, and pine nuts into rice. Season with salt and pepper. (Filling and tomatoes will keep, covered and refrigerated, for up to 1 day.)
Place tomato shells in a baking dish just large enough to hold them in a single layer. Season insides of tomato shells with salt. Fill each with about 1/3 cup rice mixture, mounding filling slightly. Top each filled tomato with a reserved tomato top. Place peppers in another baking dish, just large enough to hold them in a single layer. Fill each with about 1/2 cup rice mixture, mounding filling slightly. Add 1/2 cup water to dish with peppers.
Cover each dish with parchment, then foil. Bake until vegetables are tender and filling is heated through, 40 to 50 minutes. Serve stuffed vegetables hot, warm, or at room temperature.
For a milder filling, seed the serrano chile before mincing.