Preparation Pat ribs dry and rub Cajun seasoning all over them. Fold rack of ribs into thirds and put in a large sealable plastic bag, then marinate, chilled, at least 8 hours, or up to 1 day. Put oven rack in middle position and preheat oven to 350°F. Put rack of ribs, bone side up, in roasting pan and pour 3 cups water around ribs (water will not cover ribs). Bake, uncovered, basting with liquid and turning meat over every 30 minutes, until meaty side of ribs is browned, 2 hours total. Meanwhile, halve lemon and squeeze 1/4 cup juice into a 1 1/2- to 2-quart heavy saucepan. Add lemon halves and stir in remaining ingredients. Bring just to a boil, stirring occasionally, then reduce heat and simmer, uncovered, stirring occasionally, until thickened, about 30 minutes. Discard lemon halves. Pour off and discard water from roasting pan, then coat ribs with 2 cups sauce. Arrange ribs, meaty side up, in roasting pan and bake until ribs are tender and sauce is baked onto ribs, 40 to 50 minutes more. Serve ribs with remaining sauce. Cooks' note:Sauce can be made 1 day ahead and cooled completely, uncovered, then chilled, covered.
Preparation Pat ribs dry and rub Cajun seasoning all over them. Fold rack of ribs into thirds and put in a large sealable plastic bag, then marinate, chilled, at least 8 hours, or up to 1 day. Put oven rack in middle position and preheat oven to 350°F. Put rack of ribs, bone side up, in roasting pan and pour 3 cups water around ribs (water will not cover ribs). Bake, uncovered, basting with liquid and turning meat over every 30 minutes, until meaty side of ribs is browned, 2 hours total. Meanwhile, halve lemon and squeeze 1/4 cup juice into a 1 1/2- to 2-quart heavy saucepan. Add lemon halves and stir in remaining ingredients. Bring just to a boil, stirring occasionally, then reduce heat and simmer, uncovered, stirring occasionally, until thickened, about 30 minutes. Discard lemon halves. Pour off and discard water from roasting pan, then coat ribs with 2 cups sauce. Arrange ribs, meaty side up, in roasting pan and bake until ribs are tender and sauce is baked onto ribs, 40 to 50 minutes more. Serve ribs with remaining sauce. Cooks' note:Sauce can be made 1 day ahead and cooled completely, uncovered, then chilled, covered.