In a medium-sized bowl, combine brown rice, flour, salt, cayenne and baking powder together. Make a well in the centre of the rice mixture.
In a small bowl, beat egg yolks and milk together. Reserve egg whites. Pour liquids into well. Stir until combined. Let rest for 30 minutes, or store covered and refrigerated for up to one day.
In a medium-sized bowl, beat egg whites until soft peaks form. Fold egg whites into batter.
Heat a medium-sized skillet over medium heat. Brush lightly with oil.
Drop 1 tbsp (15 mL) of batter into the hot skillet and gently spread using back of spoon to form circles 1-1/2 inches (3.5 cm) in diameter. Repeat procedure to comfortably fill the skillet, 4 to 5 blinis at a time. Cook until bubbles appear and underside is golden, about 3 minutes. Flip and cook other side for 2 minutes. Remove blini from heat and let cool completely on wire rack. Wipe pan with paper towel and lightly brush with more oil. Repeat until all batter is used.
Top each blini with 1/2 (2 mL) to 1 tsp (5 mL) of crème fraiche, 1/2 tsp (2 mL) diced red onion, a piece of smoked salmon or trout and a sprig of dill.