Man does not live by tortilla alone. For example, there's also tequila. Tequila that's twenty years old, tequila that's a hundred years old, tequila that comes in that familiar Jose Cuervo bottle, tequila that comes in containers worthy of museum status. The tequila just keeps coming to La Cueva, a 27-year-old restaurant on East Colfax that welcomed in the millennium by adding a trendy tequila-and-margarita bar to its already substantial lineup of authentic Mexican fare. The dishes come from Norma Nu?ez, and she's justifiably proud of them -- so much so that she's produced a book of her recipes.