There are multiple solutions for your challenge. Depending on how the data is used in further steps of your app defines the best choice
Most simple solution
Single entity with the meal type as an enumeration, capturing the values Breakfast, Lunch & Diner.
If you want to show a list of reservations for a specific moment, i.e. lunch of today, then this is to simplistic.
A bit more sophisticated
The meal aka a specific moment captured in a entity with Date and type.
The reservation has a 1-* association so that you are able to select a single meal for the reservation
The page requires a reference selector to select a single meal. But the selection is done based on 2 values; the date and type.
Therefore a lookup/select page is the best suitable option out of the box.
A select page can be generated by right mouse click on the reference selector and select “Generate select page”
Showing a list of reservations per mail is now possible
More sophisticated fancy reporting
Introduction of a third entity, which captures the day.
For this approach the user selects first the Day. Where after the user can select a meal out of the list meals of that day
To achieve this, The second selector needs to be constraint to the Meals for the selected day. This can be done using constrained by.
By selecting this option only the meals of the selected Day will be selectable.
This setup allows for reporting on the Date with a list of meals and reservations. And allows to have a more flexible setup of your meals. Though my guestimation is that this is shooting with a cannonball on a fly.
Couple of things: