Adapted from two recipes, as well as users' comments:
Food Network: Grandma's Strawberry-Rhubarb Pie
Epicurious: Lattice Topped Strawberry Rhubarb Pie
Delish - Huge hit at my office. It was all gone in record time. Only use 1/2 teaspoon of cinn. and use 4 cups of rhubarb and 4 cups of strawberries and leave sugar amounts as receipe states. Use a heaping 1/4 cup of cornstarch for a nice thicker texture. Mix filling and let stand for 1 hour. Drain juice and reduce in a pan over low heat and reincorporate into filling right before putting it in the crust. After you finish the lattice top chill the pie for 15 minutes or so before baking. Bake tented with foil at 350 for 20 minutes then 40 minutes at 400. Uncover and bake until crust is golden (aprox. 20 more minutes). Make sure you place a pan lined in foil on the bottom rack to catch the drippings.
by Husberi from Seattle, WA on 07/09/09
~2.5 cups chopped red rhubarb (used 4 stalks of even thickness, 1/4 to 1/2 inch slices)
~2.5 cups cut strawberries (used ~3 small green baskets-worth from the farmers' market)
1/2 or 1/3 cup white sugar (used just over 1/3 cup Wholesome Sweeteners evaporated cane juice Organic Sugar)
1/2 cup brown sugar, light or dark (results in slightly different flavor) (used Trader Joe's brown sugar)
2 tbsp Minute tapioca (will result in small tapioca pearls unless ground) (ground ~1/2 cup in an electric coffee/spice grinder ahead of time)
1 tbsp all-purpose flour
1/2 tsp lemon zest (didn't exactly measure... from 1/2 medium lemon)
1/2 tsp lemon juice (I may have added extra, probably amounting to just under 1 tsp)
1/2 tsp ground cinnamon (used Penzey's China Cinnamon--may have added an extra tiny pinch)
1 tsp vanilla extract
2 9-inch pie crusts (used the recipe from the Tartine Bakery cookbook for flaky tart dough, prepared before preparing the filling)
Mix filling and let stand for one hour.
(I continued stirring/folding from bottom for about an hour while watching an episode of Friday Night Lights, while waiting for the crust dough to refrigerate. I made sure that filling was always covered in juice to allow flavor to remain consistent throughout filling... even though this may have been unnecessary. But it smelled amazing, so it was totally worth it.)
Drain juice and reduce in a pan over low heat. Reincorporate filling right before putting in the crust.
(It was hard to drain the juice, and there wasn't much left after it was reduced. And it was already pretty thick to begin with. Might wait to add tapioca and flour until this step next time. I only added the reduced juice on top of the filling when already in bottom crust, then spread around the top a little. I had too much filling to fit in the pie, so I sautéed some of it in the reduction pan, and shoved the rest in a makeshift galette/turnover using excess pie dough.)
Preheat the oven to 350°F.
Latticed the top crust, starting with the two longest strips criss-crossed across the center. (I used this tutorial). Used remnants of filling juice (from original bowl, not pan) to help adhere the strips to the bottom crust. Trimmed edges by running a paring knife along the edge of the 9-inch Pyrex pie plate. Used remnants of filling juice as a glaze, then sprinkled thoroughly with turbinado sugar. May mix a little cinnamon with the sugar next time.
Place pie on a parchment paper-lined pan, then place in oven.
(Used the middle rack position in the oven.)
Bake with tented foil (loosely covered, pretty much) at 350°F for 20 minutes, 400°F for 40 minutes, then uncover and bake until crust is golden (~15 to 20 more minutes).
(I followed this carefully. I think I only needed the 15 minutes.)
Let cool on wire rack or stove grates, then serve.
(Made in the afternoon, before dinner. Reheated for ~5-7 minutes at 350°F. We served ours with Clover whipped cream. Stored in an airtight container in the refrigerator. It still tasted fantastic cold.)