Thanks for the great idea. I, also, use RTM for meal planning, but with a slightly different twist.
I created a list for recipes. I have added an unscheduled item for each dish that I like to prepare. They are tagged with the type of item, beginning with an "r" - r_main-dish, r_side-dish, r_soup, r_salad, r_sauce, r-dessert, etc. for easy searching. The duration field is used to indicate the total time to prepare. The note fields contain the ingredient list and preparation instructions for each recipe.
When planning the meals for the week, I select and duplicate the recipes that I want to cook. I add a date or date-time to each new item, and move them to my "calendar" (dated items) list, which I maintain as a separate list from undated todo items. Those to know GTD will understand the reasoning for the separation, but it's not essential to this use of RTM.
To plan shopping, I cut-and-paste the ingredient list from each recipe, for that week, into the notes of a new undated task called Shopping List. I, then, check the kitchen for each item, and remove those that I already have.
The result is a meal plan with shopping list created with very little work. Since I sync RTM to my phone, it's all mobile and easy to share. I can print the Shopping List todo item, or just work from my phone.
Posted 5 months ago