Linzer cookies aren't hard -- it's a basic sandwich cookie with a jam filling. These cutters make it easy to make fancy cookies with a cutout to let the jam show through:
http://a.co/hhFiB8Y
Serious Eats is my go-to recipe site, and has a number of Linzer cookie recipes, including this one:
http://www.seriouseats.com/recipes/2011/12/linzer-cookies-hazelnut-jam-recipe.html
The rumtoertchen don't look too hard either, but are going to have a different flavor profile (rum-cherry).
The Lecker recipe:
300 g (plus extra) flour
150 g sugar
1 package vanilla sugar (Dr. Oetker is the brand I know of)
salt
1 medium egg
150 g cold butter
150 g cherry jam (I'd use a smooth one, not a chunky one)
6-7 tablespoons rum
250 g powdered sugar
2 tablespoons lemon juice
Loose translation with my annotations:
1) Mix 300 g flour, sugar, vanilla sugar, 1 pinch salt in the bowl of a stand mixer. {I would sift them together}. Add flaked butter {small pieces} and egg {I would beat first}. Mix with the dough hook until the dough comes together, then use your hands to finish kneading quickly into a smooth dough. {Use a light hand; knead with the machine and your hands just until the dough comes together. Don't overknead as you don't want the gluten to become over-developed; it will make your cookies tough.}
2) Wrap in plastic wrap and refrigerate for one hour.
3) Preheat oven to 390 F {I'd probably do 350-375}. Set out three baking sheets lined with parchment paper. Roll out the dough to a thickness of 2 mm, using a little flour on the counter to keep it from sticking. {A Silpat works really well for this, and the less flour you add the more tender your cookies will be.} Use a 5 cm round cookie cutter to cut out ~70 cookies. You will need to pick up the dough scraps, re-knead {gently!} and re-roll to get as many cookies as possible.
4) Place the cookies on the prepared sheets and bake 7-9 minutes. Let cool. {I'd transfer them to cookie racks to cool.}
5) Stir the jam and 2 tablespoons of rum together until smooth. Cover half the cookies with jam; top with the remaining cookies to make sandwiches.
6) Whisk together the powdered sugar, 4-5 tablespoons of rum {start with the lower quantity}, and lemon juice together until smooth. Using a pastry brush, apply glaze to cookies and let dry.