Quinoa - (Double if making Tuesday’s meal.) Combine quinoa with stock in a saucepan. Add some salt. Cover and bring to a boil. Lower heat, keep covered, and cook until liquid is absorbed, 8 to 10 minutes. (Can be done up to 5 days ahead)
Make garlic oil - Chop garlic. Combine garlic, olive oil, and dried oregano. (Can be done up to 5 days ahead)
Tomatoes / Cucumbers - Prep as directed. Store separately. (Can be done 1 day ahead)
Cucumbers - Whisk together vinegar and mustard. Add cucumbers. Refrigerate for at least 20 minutes and up to a day. (Can be done 1 day ahead)
Salmon - Divide into the number of portions you are planning to serve. Rinse and pat dry. Lightly salt and pepper.
Heat a skillet over medium-high heat. Add cooking oil and then salmon to heated oil. Sear for 2 minutes.
Flip salmon over and sear for an additional 2 minutes. In the pan, add tomatoes around the salmon. Drizzle garlic oil over salmon and tomatoes. Cover pan with a lid or foil.
Reduce heat to low-medium. Continue cooking salmon, covered, until it flakes easily with a fork, 4 to 7 minutes (depending on thickness).
While salmon cooks, toss cucumbers with mint. Season with some salt and pepper.
If quinoa was made ahead, reheat in the microwave (reserve half if doubled).
Serve salmon and tomatoes over quinoa. Enjoy with cucumbers on the side.