Use a sharp knife to excise the central rib from each collard leaf, reserving both parts. Stack the leaf-halves and slice them crosswise into thin ribbons; it should look like packing material. Trim the dead ends off the ribs, then cross-cut them into ¼-inch bits. Place in a separate pile.
Heat up a wok or large frying pan over high heat. Add the fat, and as soon as it shimmers, toss in the cumin seeds, and stir. 10 seconds later, add the ginger, garlic, collard rib bits, and whole red chili. Keep it moving, then in another 10 seconds, add the green chilies. 10 seconds more, and the collards and salt go in. Fry briskly until leaves are completely coated in fat and flavorings.
Toss in the tomato and keep stirring over high heat, as the leaves begin to steam in the juice. As soon as the collards are tender, stir in the lemon juice and more salt, if needed, and remove from the heat.
Serve hot, warm, or room temperature.