Technically, the flowers of the nopal or prickly pear cactus of the genus Opuntia are edible, though only part of the flower is selected for cooking. The unopened flower buds or tuna of the nopal cacti can be harvested before the bloom opens for use as a cooked vegetable. Once the flower blooms, the developing cactus berry becomes too tough for eating. Some varieties are again tasty when the fruit fully ripens.
Harvest nopal cactus tuna (or berries) before the blooms open. Use sticks to knock the berries loose from the fleshy leaves and avoid the thorns, both on the plant and on the berries.
Remove glochids--the thorn-bearing bumps on the tuna skin--by thrashing. Spread the tuna on bare ground. Cut enough green weeds or grasses to form a bundle several inches thick. Grip the stems in one hand and use the bundle of green plants as a thorn-removing broom. Sweep the leaves over the tuna repeatedly, rolling the berries on the ground. Thorns penetrate the green weed leaves and break free of the fruit.
Wash the tuna carefully in case some glochids remain. If the berries are thorn free, peel them with a paring knife before cooking. Pin prickly berries with a fork and slice off both base and tip. Slice one side end to end just through the skin and pin the meat of the berry with the tines of the fork. Peel the skin from the fruit with the paring knife.
Chop peeled tuna for adding to stir-fried recipes including onions, cilantro and other southwestern favorite vegetables. Cook until the flesh of the tuna loses its shape for a traditional vegetable medley.
Cook tuna as you would okra--the slimy juice of the berries holds seasoned corn batter well and pan fries to a drier consistency. Adding tuna to soups and stews creates a tart gumbo.