Here are the two different approaches I take with Dortmunders. Both have turned out good beers.
(I brew 6-6.5 gallons so adjust for your system.)
Version 1:
66% Pilsner Malt
31% Munich Malt
2% Melanoiden Malt
1% acidulated malt
60 min. - 2 oz. Hallertau
10 min. - 1 oz. Hallertau
0 min. - 1 oz. Hallertau
Adjust for your system, but shooting for 1.055 OG, 30 IBU's
Single Infusion mash for 75 minutes @152
90 minute boil
2124 Yeast, Big starter, 49-52 degrees for 14 days. Free rise to 67 degrees over the course of 2-3 days. Cold crash, and keg.
Mash Water - 90% RO water. Targeting the following #'s (approximately) on the last couple batches: Ca = 75, Sul = 75, Cl = 40, Bicarb = 40. I used about 2.5 grams of gypsum and 1.5 grams of CaCl.
Version 2:
This may seem a bit unorthodox, but it turns out a nice beer. Most recently, it placed 1st at NHC regional at KC.
53% Pilsner Malt
17% Munich
17% Maris Otter
8% Wheat
4% Cara pils
1% Acidulated
(Aiming for 1.055 OG)
60 min. 1 oz. Northern Brewer
15 min. 1 oz. Liberty
0 min. 1 oz. Tettnang
(aiming for 32 IBU's)
2124 yeast starter, 152 infusion mash 90 minutes, same water profile, same fermentation schedule.
Basically, my goal for Dortmunder has always sort of been "Hoppier Helles or Maltier Pilsner".... and Very, very drinkable.
Cheers!