"Greek" meatloaf and Tzatziki

Here's the inspiration: turkey meatloaf stuffed with feta.

Tzatziki:
2 cups Greek-style yogurt
about 3 cloves of garlic, minced
1/2 of an English cucumber, quartered long-ways, and then thinly sliced
1 T lemon juice
1/2 t salt
1 t dried dill weed

Mix it together, cover it, and let it sit in the fridge at least a few hours, if not overnight.

Meatloaf:
a tablespoon or two of olive oil
1 good-sized onion, chopped pretty small
about 3 cloves of garlic, minced
1 t salt
freshly ground pepper (I was going for 1/2 t, but didn't measure)
1 (10 oz) package frozen spinach, thawed and drained
3 lb. ground turkey
2 eggs
1/2 c coconut flour
2 T Worcestershire sauce
a tablespoon or two of dried oregano
1 1/2 cups (about) crumbled feta

Warm the olive oil in a fry pan over medium heat.  Add the onion, garlic, salt, and pepper.  Cook, stirring occasionally, for 15 minutes, until the onion is translucent.  
Put everything but the feta (including the onion mixture) in a big bowl, and mix it all together with your hands.
(At this point, I covered the bowl, and put it in the fridge overnight.)
Heat the oven to 325.
Line a baking sheet with parchment paper.
Divide the meat mixture into about half.  Shape the smaller half into a rectangle on the baking sheet.  Spread the crumbled feta over the rectangle, but not quite to the edges.  Cover the feta with the rest of the meat mixture.  (I patted a handful at a time into the appropriate thickness, and squished the pieces together a bit rather than try to make a big rectangle, and then I squished the edges of the rectangle together so the cheese wouldn't leak out.)
Bake 1- 1 1/4 hour, until the internal temperature is at least 160 degrees F.  (I went for 170, and it got to 180 as it rested.)
Serve with tzatziki.