Preheat oven or toaster oven to 375° F.
In a mixing bowl with dough hook attached, add in flour and salt. Stir to incorporate.
With the mixer on the slowest speed, slowly add in the canola oil. When the dough becomes pebble-like in texture, add the ice water, one spoonful at a time, until fully incorporated and the dough comes together.
Press the dough into the tart pan, making sure to cover all the edges and without any holes in the bottom.
Sprinkle the feta cheese over the entire bottom of the tart.
Top with the sliced tomatoes, arranging in a circular pattern, overlapping the edges of each slice slightly.
Sprinkle with sea salt and scatter the thyme sprigs on top.
Bake for 30 minutes, or until the edges of the tart are golden brown. Serve warm.