Lard is the traditional fat used to make many Tex-Mex flour tortillas tender.
Flour tortillas are made from wheat flour, water, salt, and a shortening or fat. Historically, lard was especially common because it produces a soft, flexible tortilla with a lightly savory flavor. The fat also helps limit gluten development, making the dough easier to roll and less tough after cooking.
Commercial and home recipes may use vegetable shortening, oil, or butter instead. These substitutions can change the flavor and texture, so “flour tortilla” does not always imply lard today.
Corn tortillas differ in both grain and process: they are made from nixtamalized maize rather than wheat flour. In Tex-Mex cooking, flour tortillas are particularly associated with burritos, breakfast tacos, and some fajitas.